void qcktrc_c ( SpiceInt tracelen,
SpiceChar * trace )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
tracelen I Maximum length of output traceback string.
trace O A traceback string.
SPICE_ERROR_MAXMOD
P Maximum traceback module count.
SPICE_ERROR_MODLEN
P Maximum module name length.
SPICE_ERROR_TRCLEN
P Maximum length of output traceback string.
-Detailed_Input
None.
-Detailed_Output
trace is a list of module names, delimited by the string,
" --> ". An example would be
"SPUD --> SPAM --> FOOBAR".
The maximum length of the returned string is given
by the parameter SPICE_ERROR_TRCLEN. The value of this
parameter includes room for the terminating null.
In general, the meaning of the trace is as follows:
The first name in the list is the name of the first
module to check in (that hasn't yet checked out). The
last name is the name of the module at the end of the
call chain; this is the last module that checked in.
The meaning of the traceback depends on the state
of the error handling mechanism. There are two
cases:
1) In RETURN mode, when an error is signaled, the
traceback at that point is saved. trcdep_c,
trcnam_c, and qcktrc_c return values
pertaining to the saved traceback.
2) In all other modes, the traceback represents
the CURRENT call chain. trcdep_c, trcnam_c,
and qcktrc_c return values pertaining to the
current trace representation.
Any module names exceeding SPICE_ERROR_MODLEN
characters in length are truncated on the right.
-Parameters
The following parameters are declared in the header file SpiceErr.h:
SPICE_ERROR_MAXMOD is the maximum number of module names that can
be accommodated in the SPICE trace stack; this
is the maximum number of names that can appear
in the output traceback.
SPICE_ERROR_MODLEN is the maximum module name length that can be
accommodated by this routine.
SPICE_ERROR_TRCLEN is the maximum length of the string returned
by this routine. The value of this parameter
includes room for the terminating null.
-Exceptions
1) If the output string pointer is null, the error SPICE(NULLPOINTER)
will be signaled.
2) If the output string has length less than 2 characters, the error
SPICE(STRINGTOOSHORT) will be signaled.
-Files
None.
-Particulars
This routine is part of the CSPICE error handling mechanism.
-Examples
1) Deliberately generate a SPICE error to demonstrate use of
this routine together with trcnam_c. We'll attempt to look up
a state vector via spkezr_c without first having loaded any
SPK files.
Example code begins here.
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Local constants
./
#define ACTION "RETURN"
/.
Local variables
./
SpiceChar * abcorr;
SpiceChar trace [ SPICE_ERROR_TRCLEN ];
SpiceChar * obsrvr;
SpiceChar * frame;
SpiceChar * target;
SpiceDouble et;
SpiceDouble lt;
SpiceDouble state [6];
/.
Set error handling action to RETURN so that this program
won't terminate when a SPICE error is signaled. Note that
the input string length argument is unused for a "SET"
operation.
./
erract_c ( "SET", 0, ACTION );
/.
Generate a SPICE error: call spkezr_c without first having
loaded an SPK file.
./
et = 0.0;
target = "Moon";
obsrvr = "Earth";
frame = "J2000";
abcorr = "NONE";
spkezr_c ( target, et, frame, abcorr, obsrvr, state, < );
if ( failed_c() )
{
/.
An error has been signaled. Fetch and display
the traceback.
./
qcktrc_c ( SPICE_ERROR_TRCLEN, trace );
printf ( "Traceback: \n%s\n", trace );
/.
Reset the error status so that CSPICE can resume normal
operation.
./
reset_c();
}
return ( 0 );
}
When this program was executed on a PC/Linux/gcc platform, the
output (which has been reformatted to fit in the available
space in this header) was:
====================================================================
============
Toolkit version: N0065
SPICE(NOLOADEDFILES) --
At least one SPK file needs to be loaded by SPKLEF before beginning
a search.
A traceback follows. The name of the highest level module is first.
spkezr_c --> SPKEZR --> SPKEZ --> SPKGEO --> SPKSFS
====================================================================
============
Traceback:
spkezr_c --> SPKEZR --> SPKEZ --> SPKGEO --> SPKSFS
-Restrictions
1) It is assumed no module names exceed SPICE_ERROR_MODLEN
characters in length.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
K.R. Gehringer (JPL)
-Version
-CSPICE Version 1.0.0, 05-NOV-2013 (NJB) (KRG)
-Index_Entries
get quick traceback
-&
*/
{ /* Begin qcktrc_c */
/*
This routine does not check in unless an input error occurs.
*/
/*
Make sure the output string has at least enough room for one output
character and a null terminator. Also check for a null pointer.
We don't use the usual CHKOSTR macro here because we must reset
the error status before signaling an error.
*/
if ( trace == NULL )
{
reset_c ();
chkin_c ( "qcktrc_c" );
setmsg_c ( "The output string pointer 'trace' is null." );
sigerr_c ( "SPICE(NULLPOINTER)" );
chkout_c ( "qcktrc_c" );
return;
}
if ( tracelen < 2 )
{
reset_c ();
chkin_c ( "qcktrc_c" );
setmsg_c ( "The output string 'trace' has length #; the "
"minimum allowed length is 2 characters." );
errint_c ( "#", tracelen );
sigerr_c ( "SPICE(STRINGTOOSHORT)" );
chkout_c ( "qcktrc_c" );
return;
}
/*
Fetch the traceback.
*/
qcktrc_ ( ( char * ) trace,
( ftnlen ) tracelen-1 );
/*
Convert the output name string to a null-terminated,
C style string.
*/
F2C_ConvertStr ( tracelen, trace );
} /* End qcktrc_c */
void gfrr_c ( ConstSpiceChar * target,
ConstSpiceChar * abcorr,
ConstSpiceChar * obsrvr,
ConstSpiceChar * relate,
SpiceDouble refval,
SpiceDouble adjust,
SpiceDouble step,
SpiceInt nintvls,
SpiceCell * cnfine,
SpiceCell * result )
/*
-Brief_I/O
Variable I/O Description
-------- --- --------------------------------------------------
SPICE_GF_CNVTOL P Convergence tolerance
target I Name of the target body.
abcorr I Aberration correction flag.
obsrvr I Name of the observing body.
relate I Relational operator.
refval I Reference value.
adjust I Adjustment value for absolute extrema searches.
step I Step size used for locating extrema and roots.
nintvls I Workspace window interval count.
cnfine I-O SPICE window to which the search is confined.
result O SPICE window containing results.
-Detailed_Input
target is the name of a target body. The target body is
an ephemeris object; its trajectory is given by
SPK data.
The string `target' is case-insensitive, and leading
and trailing blanks in `target' are not significant.
Optionally, you may supply a string containing the
integer ID code for the object. For example both
"MOON" and "301" are legitimate strings that indicate
the Moon is the target body.
The target and observer define a position vector which
points from the observer to the target; the time derivative
length of this vector is the "range rate" that serves as
the subject of the search performed by this routine.
abcorr indicates the aberration corrections to be applied to
the observer-target state vector to account for
one-way light time and stellar aberration.
Any aberration correction accepted by the SPICE
routine spkezr_c is accepted here. See the header
of spkezr_c for a detailed description of the
aberration correction options. For convenience,
the options are listed below:
"NONE" Apply no correction.
"LT" "Reception" case: correct for
one-way light time using a Newtonian
formulation.
"LT+S" "Reception" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
"CN" "Reception" case: converged
Newtonian light time correction.
"CN+S" "Reception" case: converged
Newtonian light time and stellar
aberration corrections.
"XLT" "Transmission" case: correct for
one-way light time using a Newtonian
formulation.
"XLT+S" "Transmission" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
"XCN" "Transmission" case: converged
Newtonian light time correction.
"XCN+S" "Transmission" case: converged
Newtonian light time and stellar
aberration corrections.
Case and blanks are not significant in the string
`abcorr'.
obsrvr is the name of the observing body. The observing body is
an ephemeris object; its trajectory is given by SPK
data. `obsrvr' is case-insensitive, and leading and
trailing blanks in `obsrvr' are not significant.
Optionally, you may supply a string containing the
integer ID code for the object. For example both "MOON"
and "301" are legitimate strings that indicate the Moon
is the observer.
relate is a relational operator used to define a constraint
on observer-target range rate. The result window found
by this routine indicates the time intervals where
the constraint is satisfied. Supported values of
`relate' and corresponding meanings are shown below:
">" Distance is greater than the reference
value `refval'.
"=" Distance is equal to the reference
value `refval'.
"<" Distance is less than the reference
value `refval'.
"ABSMAX" Distance is at an absolute maximum.
"ABSMIN" Distance is at an absolute minimum.
"LOCMAX" Distance is at a local maximum.
"LOCMIN" Distance is at a local minimum.
The caller may indicate that the region of interest
is the set of time intervals where the quantity is
within a specified distance of an absolute extremum.
The argument `adjust' (described below) is used to
specify this distance.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
Case is not significant in the string `relate'.
refval is the reference value used together with the argument
`relate' to define an equality or inequality to be
satisfied by the range rate between the specified target
and observer. See the discussion of `relate' above for
further information.
The units of `refval' are km/sec.
adjust is a parameter used to modify searches for absolute
extrema: when `relate' is set to "ABSMAX" or "ABSMIN" and
`adjust' is set to a positive value, gfdist_c will find
times when the observer-target range rate is within
`adjust' km/sec of the specified extreme value.
If `adjust' is non-zero and a search for an absolute
minimum `min' is performed, the result window contains
time intervals when the observer-target range rate has
values between `min' and min+adjust.
If the search is for an absolute maximum `max', the
corresponding range is from max-adjust to `max'.
`adjust' is not used for searches for local extrema,
equality or inequality conditions.
step is the step size to be used in the search. `step' must
be short enough for a search using this step size
to locate the time intervals where the specified
range rate function is monotone increasing or
decreasing. However, `step' must not be *too* short, or
the search will take an unreasonable amount of time.
The choice of `step' affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
See the discussion of the parameter SPICE_GF_CNVTOL for
details.
`step' has units of TDB seconds.
nintvls is a parameter specifying the number of intervals that
can be accommodated by each of the dynamically allocated
windows used internally by this routine. `nintvls' should
be at least as large as the number of intervals within
the search region on which the specified range rate
function is monotone increasing or decreasing. See
the Examples section below for code examples illustrating
the use of this parameter.
cnfine is a SPICE window that confines the time period over
which the specified search is conducted. `cnfine' may
consist of a single interval or a collection of
intervals.
In some cases the confinement window can be used to
greatly reduce the time period that must be searched
for the desired solution. See the Particulars section
below for further discussion.
See the Examples section below for a code example
that shows how to create a confinement window.
-Detailed_Output
cnfine is the input confinement window, updated if necessary
so the control area of its data array indicates the
window's size and cardinality. The window data are
unchanged.
result is the window of intervals, contained within the
confinement window `cnfine', on which the specified
constraint is satisfied.
If `result' is non-empty on input, its contents will be
discarded before 'gfrr_c' conducts its search.
`result' must be declared with sufficient size to capture
the full set of time intervals within the search region
on which the specified constraint is satisfied.
If the search is for local extrema, or for absolute
extrema with `adjust' set to zero, then normally each
interval of `result' will be a singleton: the left and
right endpoints of each interval will be identical.
If no times within the confinement window satisfy the
constraint, `result' will be returned with a cardinality
of zero.
-Parameters
SPICE_GF_CNVTOL
is the convergence tolerance used for finding endpoints
of the intervals comprising the result window.
SPICE_GF_CNVTOL is used to determine when binary searches
for roots should terminate: when a root is bracketed
within an interval of length SPICE_GF_CNVTOL, the root is
considered to have been found.
The accuracy, as opposed to precision, of roots found
by this routine depends on the accuracy of the input
data. In most cases, the accuracy of solutions will be
inferior to their precision.
SPICE_GF_CNVTOL is declared in the header file SpiceGF.h.
-Exceptions
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except
that if the step size is non-positive, an error is signaled
by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
wncond_c can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error will be diagnosed by a routine
in the call tree of this routine.
4) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
5) If the aberration correction specifier contains an
unrecognized value, an error is signaled by a routine in the
call tree of this routine.
6) If 'adjust' is negative, the error SPICE(VALUEOUTOFRANGE) will
signal from a routine in the call tree of this routine.
A non-zero value for 'adjust' when 'relate' has any value other than
"ABSMIN" or "ABSMAX" causes the error SPICE(INVALIDVALUE) to
signal from a routine in the call tree of this routine.
7) If either of the input body names do not map to NAIF ID
codes, an error is signaled by a routine in the call tree of
this routine.
8) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
9) If the workspace interval count is less than 1, the error
SPICE(VALUEOUTOFRANGE) will be signaled.
10) If the required amount of workspace memory cannot be
allocated, the error SPICE(MALLOCFAILURE) will be
signaled.
11) If any input string argument pointer is null, the error
SPICE(NULLPOINTER) will be signaled.
12) If any input string argument is empty, the error
SPICE(EMPTYSTRING) will be signaled.
13) If either input cell has type other than SpiceDouble,
the error SPICE(TYPEMISMATCH) is signaled.
-Files
Appropriate kernels must be loaded by the calling program before
this routine is called.
The following data are required:
- SPK data: ephemeris data for target and observer for the
time period defined by the confinement window must be
loaded. If aberration corrections are used, the states of
target and observer relative to the solar system barycenter
must be calculable from the available ephemeris data.
Typically ephemeris data are made available by loading one
or more SPK files via furnsh_c.
In all cases, kernel data are normally loaded once per program
run, NOT every time this routine is called.
-Particulars
This routine determines if the caller-specified constraint condition
on the geometric event (range rate) is satisfied for any time intervals
within the confinement window 'cnfine'. If one or more such time
intervals exist, those intervals are added to the 'result' window.
This routine provides a simpler, but less flexible interface
than does the routine gfevnt_c for conducting the searches for
observer-target range rate value events. Applications that require
support for progress reporting, interrupt handling, non-default step
or refinement functions, or non-default convergence tolerance should
call gfevnt_c rather than this routine.
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the specified
range rate function is monotone increasing and monotone decreasing.
Each of these time periods is represented by a SPICE window. Having
found these windows, all of the range rate function's local extrema
within the confinement window are known. Absolute extrema then can
be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. Since the boundary
of the solution set for any inequality constraint is contained in
the union of
- the set of points where an equality constraint is met
- the boundary points of the confinement window
the solutions of both equality and inequality constraints can be
found easily once the monotone windows have been found.
Step Size
=========
The monotone windows (described above) are found via a two-step
search process. Each interval of the confinement window is
searched as follows: first, the input step size is used to
determine the time separation at which the sign of the rate of
change of range rate will be sampled. Starting at
the left endpoint of an interval, samples will be taken at each
step. If a change of sign is found, a root has been bracketed; at
that point, the time at which the range rate is zero can be
found by a refinement process, for example, via binary search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the range rate function is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is longer than the
shortest solution interval.
Having some knowledge of the relative geometry of the target and
observer can be a valuable aid in picking a reasonable step size.
In general, the user can compensate for lack of such knowledge by
picking a very short step size; the cost is increased computation
time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
As described above, the root-finding process used by this routine
involves first bracketing roots and then using a search process to
locate them. "Roots" include times when extrema are attained and
times when the geometric quantity function is equal to a reference
value or adjusted extremum. All endpoints of the intervals comprising
the result window are either endpoints of intervals of the confinement
window or roots.
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set via the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value so that the
tolerance doesn't limit the accuracy of solutions found by this
routine. In general the accuracy of input data will be the limiting
factor.
The user may change the convergence tolerance from the default
SPICE_GF_CNVTOL value by calling the routine gfstol_c, e.g.
gfstol_c( tolerance value in seconds )
Call gfstol_c prior to calling this routine. All subsequent
searches will use the updated tolerance value.
Searches over time windows of long duration may require use of
larger tolerance values than the default: the tolerance must be
large enough so that it, when added to or subtracted from the
confinement window's lower and upper bounds, yields distinct time
values.
Setting the tolerance tighter than SPICE_GF_CNVTOL is unlikely to be
useful, since the results are unlikely to be more accurate.
Making the tolerance looser will speed up searches somewhat,
since a few convergence steps will be omitted. However, in most
cases, the step size is likely to have a much greater effect
on processing time than would the convergence tolerance.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed.
Consider the following example: suppose one wishes to find the
times when the range rate between Io and the Earth attains a global
minimum over some (lengthy) time interval. There is one local
minimum every few days. The required step size for this search
must be smaller than the shortest interval on which the range rate
is monotone increasing or decreasing; this step size will be less
than half the average time between local minima. However, we know
that a global minimum can't occur when the Jupiter-Sun-Earth
angle is greater than 90 degrees. We can use a step size of a
half year to find the time period, within our original time
interval, during which this angle is less than 90 degrees; this
time period becomes the confinement window for our Earth-Io
range rate search. This way we've used a quick (due to the large
step size) search to cut out about half of the search period over
which we must perform a slower search using a small step size.
-Examples
The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: standard.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de421.bsp Planetary ephemeris
pck00009.tpc Planet orientation and
radii
naif0009.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'de421.bsp',
'pck00009.tpc',
'naif0009.tls' )
\begintext
Example:
Determine the time windows from January 1, 2007 UTC to
April 1, 2007 UTC for which the sun-moon range rate satisfies the
relation conditions with respect to a reference value of
0.3365 km/s radians (this range rate known to occur within the
search interval). Also determine the time windows corresponding
to the local maximum and minimum range rate, and the absolute
maximum and minimum range rate during the search interval.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SpiceUsr.h"
#define MAXWIN 20000
#define TIMFMT "YYYY-MON-DD HR:MN:SC.###"
#define TIMLEN 41
#define NLOOPS 7
int main( int argc, char **argv )
{
/.
Create the needed windows. Note, one window
consists of two values, so the total number
of cell values to allocate is twice
the number of intervals.
./
SPICEDOUBLE_CELL ( result, 2*MAXWIN );
SPICEDOUBLE_CELL ( cnfine, 2 );
SpiceDouble begtim;
SpiceDouble endtim;
SpiceDouble step;
SpiceDouble adjust;
SpiceDouble refval;
SpiceDouble beg;
SpiceDouble end;
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
SpiceChar * target = "MOON";
SpiceChar * abcorr = "NONE";
SpiceChar * obsrvr = "SUN";
SpiceInt count;
SpiceInt i;
SpiceInt j;
ConstSpiceChar * relate [NLOOPS] = { "=",
"<",
">",
"LOCMIN",
"ABSMIN",
"LOCMAX",
"ABSMAX",
};
/.
Load kernels.
./
furnsh_c( "standard.tm" );
/.
Store the time bounds of our search interval in
the cnfine confinement window.
./
str2et_c( "2007 JAN 01", &begtim );
str2et_c( "2007 APR 01", &endtim );
wninsd_c ( begtim, endtim, &cnfine );
/.
Search using a step size of 1 day (in units of seconds).
The reference value is .3365 km/s. We're not using the
adjustment feature, so we set 'adjust' to zero.
./
step = spd_c();
adjust = 0.;
refval = .3365;
for ( j = 0; j < NLOOPS; j++ )
{
printf ( "Relation condition: %s \n", relate[j] );
/.
Perform the search. The SPICE window 'result' contains
the set of times when the condition is met.
./
gfrr_c ( target,
abcorr,
obsrvr,
relate[j],
refval,
adjust,
step,
MAXWIN,
&cnfine,
&result );
count = wncard_c( &result );
/.
Display the results.
./
if (count == 0 )
{
printf ( "Result window is empty.\n\n" );
}
else
{
for ( i = 0; i < count; i++ )
{
/.
Fetch the endpoints of the Ith interval
of the result window.
./
wnfetd_c ( &result, i, &beg, &end );
timout_c ( beg, TIMFMT, TIMLEN, begstr );
timout_c ( end, TIMFMT, TIMLEN, endstr );
printf ( "Start time, drdt = %s \n", begstr );
printf ( "Stop time, drdt = %s \n", endstr );
}
}
printf("\n");
}
return( 0 );
}
The program outputs:
Relation condition: =
Start time, drdt = 2007-JAN-02 00:35:19.574
Stop time, drdt = 2007-JAN-02 00:35:19.574
Start time, drdt = 2007-JAN-19 22:04:54.899
Stop time, drdt = 2007-JAN-19 22:04:54.899
Start time, drdt = 2007-FEB-01 23:30:13.428
Stop time, drdt = 2007-FEB-01 23:30:13.428
Start time, drdt = 2007-FEB-17 11:10:46.540
Stop time, drdt = 2007-FEB-17 11:10:46.540
Start time, drdt = 2007-MAR-04 15:50:19.929
Stop time, drdt = 2007-MAR-04 15:50:19.929
Start time, drdt = 2007-MAR-18 09:59:05.959
Stop time, drdt = 2007-MAR-18 09:59:05.959
Relation condition: <
Start time, drdt = 2007-JAN-02 00:35:19.574
Stop time, drdt = 2007-JAN-19 22:04:54.899
Start time, drdt = 2007-FEB-01 23:30:13.428
Stop time, drdt = 2007-FEB-17 11:10:46.540
Start time, drdt = 2007-MAR-04 15:50:19.929
Stop time, drdt = 2007-MAR-18 09:59:05.959
Relation condition: >
Start time, drdt = 2007-JAN-01 00:00:00.000
Stop time, drdt = 2007-JAN-02 00:35:19.574
Start time, drdt = 2007-JAN-19 22:04:54.899
Stop time, drdt = 2007-FEB-01 23:30:13.428
Start time, drdt = 2007-FEB-17 11:10:46.540
Stop time, drdt = 2007-MAR-04 15:50:19.929
Start time, drdt = 2007-MAR-18 09:59:05.959
Stop time, drdt = 2007-APR-01 00:00:00.000
Relation condition: LOCMIN
Start time, drdt = 2007-JAN-11 07:03:58.988
Stop time, drdt = 2007-JAN-11 07:03:58.988
Start time, drdt = 2007-FEB-10 06:26:15.439
Stop time, drdt = 2007-FEB-10 06:26:15.439
Start time, drdt = 2007-MAR-12 03:28:36.404
Stop time, drdt = 2007-MAR-12 03:28:36.404
Relation condition: ABSMIN
Start time, drdt = 2007-JAN-11 07:03:58.988
Stop time, drdt = 2007-JAN-11 07:03:58.988
Relation condition: LOCMAX
Start time, drdt = 2007-JAN-26 02:27:33.766
Stop time, drdt = 2007-JAN-26 02:27:33.766
Start time, drdt = 2007-FEB-24 09:35:07.816
Stop time, drdt = 2007-FEB-24 09:35:07.816
Start time, drdt = 2007-MAR-25 17:26:56.150
Stop time, drdt = 2007-MAR-25 17:26:56.150
Relation condition: ABSMAX
Start time, drdt = 2007-MAR-25 17:26:56.150
Stop time, drdt = 2007-MAR-25 17:26:56.150
-Restrictions
1) The kernel files to be used by this routine must be loaded
(normally using the CSPICE routine furnsh_c) before this
routine is called.
2) This routine has the side effect of re-initializing the
range rate quantity utility package. Callers may themselves
need to re-initialize the range rate quantity utility
package after calling this routine.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
E.D. Wright (JPL)
-Version
-CSPICE Version 1.0.1, 28-FEB-2013 (NJB) (EDW)
Header was updated to discuss use of gfstol_c.
Edit to comments to correct search description.
Edits to Example section, proper description of "standard.tm"
meta kernel.
-CSPICE Version 1.0.0, 26-AUG-2009 (EDW) (NJB)
-Index_Entries
GF range rate search
-&
*/
{ /* Begin gfrr_c */
/*
Local variables
*/
doublereal * work;
static SpiceInt nw = SPICE_GF_NWRR;
SpiceInt nBytes;
/*
Participate in error tracing.
*/
chkin_c ( "gfrr_c" );
/*
Make sure cell data types are d.p.
*/
CELLTYPECHK2 ( CHK_STANDARD, "gfrr_c", SPICE_DP, cnfine, result );
/*
Initialize the input cells if necessary.
*/
CELLINIT2 ( cnfine, result );
/*
Check the input strings to make sure each pointer is non-null
and each string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "gfrr_c", target );
CHKFSTR ( CHK_STANDARD, "gfrr_c", abcorr );
CHKFSTR ( CHK_STANDARD, "gfrr_c", obsrvr );
CHKFSTR ( CHK_STANDARD, "gfrr_c", relate );
/*
Check the workspace size; some mallocs have a violent
dislike for negative allocation amounts. To be safe,
rule out a count of zero intervals as well.
*/
if ( nintvls < 1 )
{
setmsg_c ( "The specified workspace interval count # was "
"less than the minimum allowed value of one (1)." );
errint_c ( "#", nintvls );
sigerr_c ( "SPICE(VALUEOUTOFRANGE)" );
chkout_c ( "gfrr_c" );
return;
}
/*
Allocate the workspace. 'nintvls' indicates the maximum number of
intervals returned in 'result'. An interval consists of
two values.
*/
nintvls = 2 * nintvls;
nBytes = ( nintvls + SPICE_CELL_CTRLSZ ) * nw * sizeof(SpiceDouble);
work = (doublereal *) alloc_SpiceMemory( nBytes );
if ( !work )
{
setmsg_c ( "Workspace allocation of # bytes failed due to "
"malloc failure" );
errint_c ( "#", nBytes );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "gfrr_c" );
return;
}
/*
Let the f2'd routine do the work.
*/
gfrr_( ( char * ) target,
( char * ) abcorr,
( char * ) obsrvr,
( char * ) relate,
( doublereal * ) &refval,
( doublereal * ) &adjust,
( doublereal * ) &step,
( doublereal * ) (cnfine->base),
( integer * ) &nintvls,
( integer * ) &nw,
( doublereal * ) work,
( doublereal * ) (result->base),
( ftnlen ) strlen(target),
( ftnlen ) strlen(abcorr),
( ftnlen ) strlen(obsrvr),
( ftnlen ) strlen(relate) );
/*
De-allocate the workspace.
*/
free_SpiceMemory( work );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, result ) ;
}
ALLOC_CHECK;
chkout_c ( "gfrr_c" );
} /* End gfrr_c */
void insrtc_c ( ConstSpiceChar * item,
SpiceCell * set )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
item I Item to be inserted.
set I/O Insertion set.
-Detailed_Input
item is an item which is to be inserted into the specified
set. item may or may not already be an element of the
set. Trailing blanks in item are not significant.
set is a CSPICE set. set must be declared as a character
SpiceCell.
On input, set may or may not contain the input item
as an element.
-Detailed_Output
set on output contains the union of the input set and
the singleton set containing the input item.
-Parameters
None.
-Exceptions
1) If the input set argument is a SpiceCell of type other than
character, the error SPICE(TYPEMISMATCH) is signaled.
2) If the insertion of the element into the set causes an excess
of elements, the error SPICE(SETEXCESS) is signaled.
3) If the input set argument does not qualify as a CSPICE set,
the error SPICE(NOTASET) will be signaled. CSPICE sets have
their data elements sorted in increasing order and contain
no duplicate data elements.
4) If the input string pointer is null, the error SPICE(NULLPOINTER)
is signaled.
-Files
None.
-Particulars
None.
-Examples
1) In the following example, the element "PLUTO" is removed from
the character set planets and inserted into the character set
asteroids.
#include "SpiceUsr.h"
.
.
.
/.
Declare the sets with string length NAMLEN and with maximum
number of elements MAXSIZ.
./
SPICECHAR_CELL ( planets, MAXSIZ, NAMLEN );
SPICECHAR_CELL ( asteroids, MAXSIZ, NAMLEN );
.
.
.
removc_c ( "PLUTO", &planets );
insrtc_c ( "PLUTO", &asteroids );
If "PLUTO" is not an element of planets, then the contents of
planets are not changed. Similarly, if "PLUTO" is already an
element of asteroids, the contents of asteroids remain unchanged.
Because inserting an element into a set can increase the
cardinality of the set, an error may occur in the insertion
routines.
-Restrictions
1) String comparisons performed by this routine are Fortran-style:
trailing blanks in the input set or key value are ignored.
This gives consistent behavior with CSPICE code generated by
the f2c translator, as well as with the Fortran SPICE Toolkit.
Note that this behavior is not identical to that of the ANSI
C library functions strcmp and strncmp.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
C.A. Curzon (JPL)
W.L. Taber (JPL)
I.M. Underwood (JPL)
-Version
-CSPICE Version 2.1.0, 07-MAR-2009 (NJB)
This file now includes the header file f2cMang.h.
This header supports name mangling of f2c library
functions.
-CSPICE Version 2.0.0, 01-NOV-2005 (NJB)
Bug fix: when the item to be inserted would, after
truncation to the set's string length, match an item
already in the set, no insertion is performed. Previously
the truncated string was inserted, corrupting the set.
Long error message was updated to include size of
set into which insertion was attempted.
-CSPICE Version 1.0.0, 21-AUG-2002 (NJB) (CAC) (WLT) (IMU)
-Index_Entries
insert an item into a character set
-&
*/
{
/*
f2c library utility prototypes
*/
extern integer s_cmp (char *a, char *b, ftnlen la, ftnlen lb );
/*
Local macros
*/
#define ARRAY( i ) ( (SpiceChar *)(set->data) + (i)*(set->length) )
/*
local variables
*/
SpiceBoolean inSet;
SpiceChar * cdata;
SpiceInt i;
SpiceInt loc;
SpiceInt slen;
/*
Use discovery check-in.
Check the input string pointer to make sure it's not null.
*/
CHKPTR ( CHK_DISCOVER, "insrtc_c", item );
/*
Make sure we're working with a character cell.
*/
CELLTYPECHK ( CHK_DISCOVER, "insrtc_c", SPICE_CHR, set );
/*
Make sure the input cell is a set.
*/
CELLISSETCHK ( CHK_DISCOVER, "insrtc_c", set );
/*
Initialize the set if it's not already initialized.
*/
CELLINIT ( set );
/*
Let slen be the effective string length of the input item.
Characters beyond the string length of the set are ignored.
*/
slen = mini_c ( 2, set->length, strlen(item) );
/*
Is the item already in the set? If not, it needs to be inserted.
*/
cdata = (SpiceChar *) (set->data);
/*
The following call will give the location of the last element
less than or equal to the item to be inserted. If the item
differs from an element of the set only in characters that would
be truncated, no insertion will occur. Even in this case, the
insertion point `loc' returned by lstlec_c will be correct.
*/
loc = lstlec_c ( item, set->card, set->length, cdata );
inSet = ( loc > -1 )
&& ( s_cmp( (SpiceChar *)item, ARRAY(loc),
slen, strlen(ARRAY(loc)) ) == 0 );
if ( inSet )
{
return;
}
/*
It's an error if the set has no room left.
*/
if ( set->card == set->size )
{
chkin_c ( "insrtc_c" );
setmsg_c ( "An element could not be inserted into the set "
"due to lack of space; set size is #." );
errint_c ( "#", set->size );
sigerr_c ( "SPICE(SETEXCESS)" );
chkout_c ( "insrtc_c" );
return;
}
/*
Make room by moving the items that come after index loc in the set.
Insert the item after index loc.
*/
for ( i = (set->card); i > (loc+1); i-- )
{
SPICE_CELL_SET_C( ARRAY(i-1), i, set );
}
/*
This insertion macro will truncate the item to be inserted, if
necessary. The input item will be null-terminated.
*/
SPICE_CELL_SET_C( item, loc+1, set );
/*
Increment the set's cardinality.
*/
(set->card) ++;
}
void gfuds_c ( void ( * udfunc ) ( SpiceDouble et,
SpiceDouble * value ),
void ( * udqdec ) ( void ( * udfunc )
( SpiceDouble et,
SpiceDouble * value ),
SpiceDouble et,
SpiceBoolean * isdecr ),
ConstSpiceChar * relate,
SpiceDouble refval,
SpiceDouble adjust,
SpiceDouble step,
SpiceInt nintvls,
SpiceCell * cnfine,
SpiceCell * result )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
udfunc I Name of the routine that computes the scalar value
of interest at some time.
udqdec I Name of the routine that computes whether the
current state is decreasing.
relate I Operator that either looks for an extreme value
(max, min, local, absolute) or compares the
geometric quantity value and a number.
refval I Value used as reference for geometric quantity
condition.
adjust I Allowed variation for absolute extremal
geometric conditions.
step I Step size used for locating extrema and roots.
nintvls I Workspace window interval count
cnfine I-O SPICE window to which the search is restricted.
result O SPICE window containing results.
-Detailed_Input
udfunc the name of the external routine that returns the
value of the scalar quantity of interest at time ET.
The calling sequence for "udfunc" is:
udfunc ( et, &value )
where:
et an input double precision value
representing the TDB ephemeris seconds time
at which to determine the scalar value.
value is the value of the geometric quantity
at 'et'.
udqdec the name of the external routine that determines if
the scalar quantity calculated by "udfunc" is decreasing.
The calling sequence:
udqdec ( et, &isdecr )
where:
et an input double precision value representing
the TDB ephemeris seconds time at at which
to determine the time derivative of 'udfunc'.
isdecr a logical variable indicating whether
or not the scalar value returned by udfunc
is decreasing. 'isdecr' returns true if the
time derivative of "udfunc" at 'et' is negative.
relate the scalar string comparison operator indicating
the numeric constraint of interest. Values are:
">" value of scalar quantity greater than some
reference (refval).
"=" value of scalar quantity equal to some
reference (refval).
"<" value of scalar quantity less than some
reference (refval).
"ABSMAX" The scalar quantity is at an absolute
maximum.
"ABSMIN" The scalar quantity is at an absolute
minimum.
"LOCMAX" The scalar quantity is at a local
maximum.
"LOCMIN" The scalar quantity is at a local
minimum.
The caller may indicate that the region of interest
is the set of time intervals where the quantity is
within a specified distance of an absolute extremum.
The argument 'adjust' (described below) is used to
specified this distance.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
relate is insensitive to case, leading and
trailing blanks.
refval is the reference value used to define an equality or
inequality to satisfied by the scalar quantity.
The units of refval are those of the scalar quantity.
adjust the amount by which the quantity is allowed to vary
from an absolute extremum.
If the search is for an absolute minimum is performed,
the resulting window contains time intervals when the
geometric quantity value has values between ABSMIN and
ABSMIN + adjust.
If the search is for an absolute maximum, the
corresponding range is between ABSMAX - adjust and
ABSMAX.
'adjust' is not used for searches for local extrema,
equality or inequality conditions and must have value
zero for such searches.
step the double precision time step size to use in
the search.
'step' must be short enough to for a search using this
step size to locate the time intervals where the
scalar quantity function is monotone increasing or
decreasing. However, 'step' must not be *too* short,
or the search will take an
The choice of 'step' affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
See the discussion of the parameter SPICE_GF_CNVTOL for
details.
'step' has units of TDB seconds.
nintvls an integer value specifying the number of intervals in the
the internal workspace array used by this routine. 'nintvls'
should be at least as large as the number of intervals
within the search region on which the specified observer-target
vector coordinate function is monotone increasing or decreasing.
It does no harm to pick a value of 'nintvls' larger than the
minimum required to execute the specified search, but if chosen
too small, the search will fail.
cnfine a double precision SPICE window that confines the time
period over which the specified search is conducted.
cnfine may consist of a single interval or a collection
of intervals.
In some cases the confinement window can be used to
greatly reduce the time period that must be searched
for the desired solution. See the Particulars section
below for further discussion.
See the Examples section below for a code example
that shows how to create a confinement window.
-Detailed_Output
cnfine is the input confinement window, updated if necessary
so the control area of its data array indicates the
window's size and cardinality. The window data are
unchanged.
result is a SPICE window representing the set of time
intervals, within the confinement period, when the
specified geometric event occurs.
If `result' is non-empty on input, its contents
will be discarded before gfuds_c conducts its
search.
-Parameters
None.
-Exceptions
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except
that if the step size is non-positive, an error is signaled
by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
wncond_c can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error will be diagnosed by a routine
in the call tree of this routine.
4) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
5) If 'adjust' is negative, the error SPICE(VALUEOUTOFRANGE) will
signal from a routine in the call tree of this routine.
A non-zero value for 'adjust' when 'relate' has any value other than
"ABSMIN" or "ABSMAX" causes the error SPICE(INVALIDVALUE) to
signal from a routine in the call tree of this routine.
6) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
7) If the workspace interval count is less than 1, the error
SPICE(VALUEOUTOFRANGE) will be signaled.
8) If the required amount of workspace memory cannot be
allocated, the error SPICE(MALLOCFAILURE) will be
signaled.
9) If any input string argument pointer is null, the error
SPICE(NULLPOINTER) will be signaled.
10) If any input string argument is empty, the error
SPICE(EMPTYSTRING) will be signaled.
11) If either input cell has type other than SpiceDouble,
the error SPICE(TYPEMISMATCH) is signaled.
-Files
Appropriate kernels must be loaded by the calling program before
this routine is called.
If the scalar function requires access to ephemeris data:
- SPK data: ephemeris data for any body over the
time period defined by the confinement window must be
loaded. If aberration corrections are used, the states of
target and observer relative to the solar system barycenter
must be calculable from the available ephemeris data.
Typically ephemeris data are made available by loading one
or more SPK files via furnsh_c.
- If non-inertial reference frames are used, then PCK
files, frame kernels, C-kernels, and SCLK kernels may be
needed.
In all cases, kernel data are normally loaded once per program
run, NOT every time this routine is called.
-Particulars
This routine provides a simpler, but less flexible interface
than does the routine zzgfrel_ for conducting searches for events
corresponding to an arbitrary user defined scalar quantity
function. Applications that require support for progress
reporting, interrupt handling, non-default step or refinement
functions, or non-default convergence tolerance should call
zzgfrel_ rather than this routine.
This routine determines a set of one or more time intervals
within the confinement window when the scalar function
satisfies a caller-specified constraint. The resulting set of
intervals is returned as a SPICE window.
udqdec Default Template
=======================
The user must supply a routine to determine whether sign of the
time derivative of udfunc is positive or negative at 'et'. For
cases where udfunc is numerically well behaved, the user
may find it convenient to use a routine based on the below
template. uddc_c determines the truth of the expression
d (udfunc)
-- < 0
dt
using the library routine uddf_c to numerically calculate the
derivative of udfunc using a three-point estimation. Use
of gfdecr requires only changing the "udfunc" argument
to that of the user provided scalar function passed to gfuds_c
and defining the differential interval size, 'dt'. Please see
the Examples section for an example of gfdecr use.
void gfdecr ( SpiceDouble et, SpiceBoolean * isdecr )
{
SpiceDouble dt = h, double precision interval size;
uddc_c( udfunc, uddf_c, et, dt, isdecr );
return;
}
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the specified
scalar function is monotone increasing and monotone
decreasing. Each of these time periods is represented by a SPICE
window. Having found these windows, all of the quantity
function's local extrema within the confinement window are known.
Absolute extrema then can be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. Since the boundary
of the solution set for any inequality constraint is the set
of points where an equality constraint is met, the solutions of
both equality and inequality constraints can be found easily
once the monotone windows have been found.
Step Size
=========
The monotone windows (described above) are found using a two-step
search process. Each interval of the confinement window is
searched as follows: first, the input step size is used to
determine the time separation at which the sign of the rate of
change of quantity function will be sampled. Starting at
the left endpoint of an interval, samples will be taken at each
step. If a change of sign is found, a root has been bracketed; at
that point, the time at which the time derivative of the quantity
function is zero can be found by a refinement process, for
example, using a binary search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the quantity function is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is shorter than the
shortest solution interval.
Having some knowledge of the relative geometry of the targets and
observer can be a valuable aid in picking a reasonable step size.
In general, the user can compensate for lack of such knowledge by
picking a very short step size; the cost is increased computation
time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set via the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value so that the
tolerance doesn't become the limiting factor in the accuracy of
solutions found by this routine. In general the accuracy of input
data will be the limiting factor.
Making the tolerance tighter than SPICE_GF_CNVTOL is unlikely to
be useful, since the results are unlikely to be more accurate.
Making the tolerance looser will speed up searches somewhat,
since a few convergence steps will be omitted. However, in most
cases, the step size is likely to have a much greater affect
on processing time than would the convergence tolerance.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed.
-Examples
The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
Conduct a search on the range-rate of the vector from the Sun
to the Moon. Define a function to calculate the value.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: standard.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
\begindata
KERNELS_TO_LOAD = ( 'de414.bsp',
'pck00008.tpc',
'naif0009.tls' )
\begintext
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SpiceUsr.h"
#include "SpiceZfc.h"
#include "SpiceZad.h"
#define MAXWIN 20000
#define TIMFMT "YYYY-MON-DD HR:MN:SC.###"
#define TIMLEN 41
#define NLOOPS 7
void gfq ( SpiceDouble et, SpiceDouble * value );
void gfdecrx ( void ( * udfunc ) ( SpiceDouble et,
SpiceDouble * value ),
SpiceDouble et,
SpiceBoolean * isdecr );
doublereal dvnorm_(doublereal *state);
int main( int argc, char **argv )
{
/.
Create the needed windows. Note, one interval
consists of two values, so the total number
of cell values to allocate is twice
the number of intervals.
./
SPICEDOUBLE_CELL ( result, 2*MAXWIN );
SPICEDOUBLE_CELL ( cnfine, 2 );
SpiceDouble begtim;
SpiceDouble endtim;
SpiceDouble step;
SpiceDouble adjust;
SpiceDouble refval;
SpiceDouble beg;
SpiceDouble end;
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
SpiceInt count;
SpiceInt i;
SpiceInt j;
ConstSpiceChar * relate [NLOOPS] = { "=",
"<",
">",
"LOCMIN",
"ABSMIN",
"LOCMAX",
"ABSMAX"
};
printf( "Compile date %s, %s\n\n", __DATE__, __TIME__ );
/.
Load kernels.
./
furnsh_c( "standard.tm" );
/.
Store the time bounds of our search interval in the 'cnfine'
confinement window.
./
str2et_c( "2007 JAN 01", &begtim );
str2et_c( "2007 APR 01", &endtim );
wninsd_c ( begtim, endtim, &cnfine );
/.
Search using a step size of 1 day (in units of seconds). The reference
value is .3365 km/s. We're not using the adjustment feature, so
we set 'adjust' to zero.
./
step = spd_c();
adjust = 0.;
refval = .3365;
for ( j = 0; j < NLOOPS; j++ )
{
printf ( "Relation condition: %s \n", relate[j] );
/.
Perform the search. The SPICE window 'result' contains
the set of times when the condition is met.
./
gfuds_c ( gfq,
gfdecrx,
relate[j],
refval,
adjust,
step,
MAXWIN,
&cnfine,
&result );
count = wncard_c( &result );
/.
Display the results.
./
if (count == 0 )
{
printf ( "Result window is empty.\n\n" );
}
else
{
for ( i = 0; i < count; i++ )
{
/.
Fetch the endpoints of the Ith interval
of the result window.
./
wnfetd_c ( &result, i, &beg, &end );
timout_c ( beg, TIMFMT, TIMLEN, begstr );
timout_c ( end, TIMFMT, TIMLEN, endstr );
printf ( "Start time, drdt = %s \n", begstr );
printf ( "Stop time, drdt = %s \n", endstr );
}
}
printf("\n");
}
kclear_c();
return( 0 );
}
/.
The user defined functions required by GFUDS.
gfq for udfunc
gfdecr for udqdec
./
/.
-Procedure Procedure gfq
./
void gfq ( SpiceDouble et, SpiceDouble * value )
/.
-Abstract
User defined geometric quantity function. In this case,
the range from the sun to the Moon at TDB time 'et'.
./
{
/. Initialization ./
SpiceInt targ = 301;
SpiceInt obs = 10;
SpiceChar * ref = "J2000";
SpiceChar * abcorr = "NONE";
SpiceDouble state [6];
SpiceDouble lt;
/.
Retrieve the vector from the Sun to the Moon in the J2000
frame, without aberration correction.
./
spkez_c ( targ, et, ref, abcorr, obs, state, < );
/.
Calculate the scalar range rate corresponding the
'state' vector.
./
*value = dvnorm_( state );
return;
}
/.
-Procedure gfdecrx
./
void gfdecrx ( void ( * udfunc ) ( SpiceDouble et,
SpiceDouble * value ),
SpiceDouble et,
SpiceBoolean * isdecr )
/.
-Abstract
User defined function to detect if the function derivative
is negative (the function is decreasing) at TDB time 'et'.
./
{
SpiceDouble dt = 10.;
/.
Determine if "udfunc" is decreasing at 'et'.
uddc_c - the GF function to determine if
the derivative of the user defined
function is negative at 'et'.
uddf_c - the SPICE function to numerically calculate the
derivative of 'udfunc' at 'et' for the
interval [et-dt, et+dt].
./
uddc_c( udfunc, et, dt, isdecr );
return;
}
The program outputs:
Relation condition: =
Start time, drdt = 2007-JAN-02 00:35:19.574
Stop time, drdt = 2007-JAN-02 00:35:19.574
Start time, drdt = 2007-JAN-19 22:04:54.899
Stop time, drdt = 2007-JAN-19 22:04:54.899
Start time, drdt = 2007-FEB-01 23:30:13.428
Stop time, drdt = 2007-FEB-01 23:30:13.428
Start time, drdt = 2007-FEB-17 11:10:46.540
Stop time, drdt = 2007-FEB-17 11:10:46.540
Start time, drdt = 2007-MAR-04 15:50:19.929
Stop time, drdt = 2007-MAR-04 15:50:19.929
Start time, drdt = 2007-MAR-18 09:59:05.959
Stop time, drdt = 2007-MAR-18 09:59:05.959
Relation condition: <
Start time, drdt = 2007-JAN-02 00:35:19.574
Stop time, drdt = 2007-JAN-19 22:04:54.899
Start time, drdt = 2007-FEB-01 23:30:13.428
Stop time, drdt = 2007-FEB-17 11:10:46.540
Start time, drdt = 2007-MAR-04 15:50:19.929
Stop time, drdt = 2007-MAR-18 09:59:05.959
Relation condition: >
Start time, drdt = 2007-JAN-01 00:00:00.000
Stop time, drdt = 2007-JAN-02 00:35:19.574
Start time, drdt = 2007-JAN-19 22:04:54.899
Stop time, drdt = 2007-FEB-01 23:30:13.428
Start time, drdt = 2007-FEB-17 11:10:46.540
Stop time, drdt = 2007-MAR-04 15:50:19.929
Start time, drdt = 2007-MAR-18 09:59:05.959
Stop time, drdt = 2007-APR-01 00:00:00.000
Relation condition: LOCMIN
Start time, drdt = 2007-JAN-11 07:03:58.988
Stop time, drdt = 2007-JAN-11 07:03:58.988
Start time, drdt = 2007-FEB-10 06:26:15.439
Stop time, drdt = 2007-FEB-10 06:26:15.439
Start time, drdt = 2007-MAR-12 03:28:36.404
Stop time, drdt = 2007-MAR-12 03:28:36.404
Relation condition: ABSMIN
Start time, drdt = 2007-JAN-11 07:03:58.988
Stop time, drdt = 2007-JAN-11 07:03:58.988
Relation condition: LOCMAX
Start time, drdt = 2007-JAN-26 02:27:33.766
Stop time, drdt = 2007-JAN-26 02:27:33.766
Start time, drdt = 2007-FEB-24 09:35:07.816
Stop time, drdt = 2007-FEB-24 09:35:07.816
Start time, drdt = 2007-MAR-25 17:26:56.150
Stop time, drdt = 2007-MAR-25 17:26:56.150
Relation condition: ABSMAX
Start time, drdt = 2007-MAR-25 17:26:56.150
Stop time, drdt = 2007-MAR-25 17:26:56.150
-Restrictions
1) Any kernel files required by this routine must be loaded
before this routine is called.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
E.D. Wright (JPL)
-Version
-CSPICE Version 1.0.0, 22-FEB-2010 (EDW)
-Index_Entries
GF user defined scalar function search
-&
*/
{ /* Begin gfuds_c */
/*
Local variables
*/
doublereal * work;
static SpiceInt nw = SPICE_GF_NWMAX;
SpiceInt nBytes;
/*
Participate in error tracing.
*/
if ( return_c() )
{
return;
}
chkin_c ( "gfuds_c" );
/*
Make sure cell data types are d.p.
*/
CELLTYPECHK2 ( CHK_STANDARD, "gfuds_c", SPICE_DP, cnfine, result );
/*
Initialize the input cells if necessary.
*/
CELLINIT2 ( cnfine, result );
/*
Check the other input strings to make sure each pointer is non-null
and each string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "gfuds_c", relate );
/*
Store the input function pointers so these functions can be
called by the GF adapters.
*/
zzadsave_c ( UDFUNC, (void *)(udfunc) );
zzadsave_c ( UDQDEC, (void *)(udqdec) );
/*
Check the workspace size; some mallocs have a violent
dislike for negative allocation amounts. To be safe,
rule out a count of zero intervals as well.
*/
if ( nintvls < 1 )
{
setmsg_c ( "The specified workspace interval count # was "
"less than the minimum allowed value of one (1)." );
errint_c ( "#", nintvls );
sigerr_c ( "SPICE(VALUEOUTOFRANGE)" );
chkout_c ( "gfuds_c" );
return;
}
/*
Allocate the workspace. 'nintvls' indicates the maximum number of
intervals returned in 'result'. An interval consists of
two values.
*/
nintvls = 2 * nintvls;
nBytes = (nintvls + SPICE_CELL_CTRLSZ ) * nw * sizeof(SpiceDouble);
work = (doublereal *) alloc_SpiceMemory( nBytes );
if ( !work )
{
setmsg_c ( "Workspace allocation of # bytes failed due to "
"malloc failure" );
errint_c ( "#", nBytes );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "gfuds_c" );
return;
}
/*
Let the f2c'd routine do the work.
We pass the adapter functions, not those provided as inputs,
to the f2c'd routine:
zzadfunc_c adapter for udfunc
zzadqdec_c '' udqdec
*/
(void) gfuds_( ( U_fp ) zzadfunc_c,
( U_fp ) zzadqdec_c,
( char * ) relate,
( doublereal * ) &refval,
( doublereal * ) &adjust,
( doublereal * ) &step,
( doublereal * ) (cnfine->base),
( integer * ) &nintvls,
( integer * ) &nw,
( doublereal * ) work,
( doublereal * ) (result->base),
( ftnlen ) strlen(relate) );
/*
Always free dynamically allocated memory.
*/
free_SpiceMemory( work );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, result );
}
ALLOC_CHECK;
chkout_c ( "gfuds_c" );
} /* End gfuds_c */
void gfsubc_c ( ConstSpiceChar * target,
ConstSpiceChar * fixref,
ConstSpiceChar * method,
ConstSpiceChar * abcorr,
ConstSpiceChar * obsrvr,
ConstSpiceChar * crdsys,
ConstSpiceChar * coord,
ConstSpiceChar * relate,
SpiceDouble refval,
SpiceDouble adjust,
SpiceDouble step,
SpiceInt nintvls,
SpiceCell * cnfine,
SpiceCell * result )
/*
-Brief_I/O
Variable I/O Description
-------- --- --------------------------------------------------
SPICE_GF_CNVTOL
P Convergence tolerance.
target I Name of the target body
fixref I Body fixed frame associated with 'target'
method I Name of method type for subpoint calculation
abcorr I Aberration correction flag
obsrvr I Name of the observing body
crdsys I Name of the coordinate system containing 'coord'
coord I Name of the coordinate of interest
relate I Operator that either looks for an extreme value
(max, min, local, absolute) or compares the
coordinate value and refval
refval I Reference value
adjust I Adjustment value for absolute extrema searches
step I Step size used for locating extrema and roots
nintvls I Workspace window interval count
cnfine I-O SPICE window to which the search is restricted
result O SPICE window containing results
-Detailed_Input
target the string name of a target body. Optionally, you may
supply the integer ID code for the object as an
integer string. For example both 'MOON' and '301'
are legitimate strings that indicate the moon is the
target body.
The target and observer define a position vector
that points from the observer to the target.
fixref the string name of the body-fixed, body-centered
reference frame associated with the target body target.
The SPICE frame subsystem must recognize the 'fixref' name.
method the string name of the method to use for the subpoint
calculation. The accepted values for method:
'Near point: ellipsoid' The sub-observer point
computation uses a
triaxial ellipsoid to
model the surface of the
target body. The
sub-observer point is
defined as the nearest
point on the target
relative to the
observer.
'Intercept: ellipsoid' The sub-observer point
computation uses a
triaxial ellipsoid to
model the surface of the
target body. The
sub-observer point is
defined as the target
surface intercept of the
line containing the
observer and the
target's center.
The method string lacks sensitivity to case, embedded, leading
and trailing blanks.
abcorr the string description of the aberration corrections to apply
to the state evaluations to account for one-way light time
and stellar aberration.
This routine accepts the same aberration corrections as does
the SPICE routine SPKEZR. See the header of SPKEZR for a
detailed description of the aberration correction options.
For convenience, the options are listed below:
'NONE' Apply no correction.
'LT' "Reception" case: correct for
one-way light time using a Newtonian
formulation.
'LT+S' "Reception" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
'CN' "Reception" case: converged
Newtonian light time correction.
'CN+S' "Reception" case: converged
Newtonian light time and stellar
aberration corrections.
'XLT' "Transmission" case: correct for
one-way light time using a Newtonian
formulation.
'XLT+S' "Transmission" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
'XCN' "Transmission" case: converged
Newtonian light time correction.
'XCN+S' "Transmission" case: converged
Newtonian light time and stellar
aberration corrections.
The abcorr string lacks sensitivity to case, and to embedded,
leading and trailing blanks.
obsrvr the string naming the observing body. Optionally, you
may supply the ID code of the object as an integer
string. For example, both 'EARTH' and '399' are
legitimate strings to supply to indicate the
observer is Earth.
crdsys the string name of the coordinate system for which the
coordinate of interest is a member.
coord the string name of the coordinate of interest in crdsys.
The supported coordinate systems and coordinate names are:
The supported coordinate systems and coordinate names are:
Coordinate System (CRDSYS) Coordinates (COORD) Range
'RECTANGULAR' 'X'
'Y'
'Z'
'LATITUDINAL' 'RADIUS'
'LONGITUDE' (-Pi,Pi]
'LATITUDE' [-Pi/2,Pi/2]
'RA/DEC' 'RANGE'
'RIGHT ASCENSION' [0,2Pi)
'DECLINATION' [-Pi/2,Pi/2]
'SPHERICAL' 'RADIUS'
'COLATITUDE' [0,Pi]
'LONGITUDE' (-Pi,Pi]
'CYLINDRICAL' 'RADIUS'
'LONGITUDE' [0,2Pi)
'Z'
'GEODETIC' 'LONGITUDE' (-Pi,Pi]
'LATITUDE' [-Pi/2,Pi/2]
'ALTITUDE'
'PLANETOGRAPHIC' 'LONGITUDE' [0,2Pi)
'LATITUDE' [-Pi/2,Pi/2]
'ALTITUDE'
The ALTITUDE coordinates have a constant value
of zero +/- roundoff for ellipsoid targets.
Limit searches for coordinate events in the GEODETIC and
PLANETOGRAPHIC coordinate systems to TARGET bodies with
axial symmetry in the equatorial plane, i.e. equality
of the body X and Y radii (oblate or prolate spheroids).
relate the string or character describing the relational operator
used to define a constraint on the selected coordinate of the
subpoint vector. The result window found by this routine
indicates the time intervals where the constraint is satisfied.
Supported values of relate and corresponding meanings are
shown below:
'>' Separation is greater than the reference
value refval.
'=' Separation is equal to the reference
value refval.
'<' Separation is less than the reference
value refval.
'ABSMAX' Separation is at an absolute maximum.
'ABSMIN' Separation is at an absolute minimum.
'LOCMAX' Separation is at a local maximum.
'LOCMIN' Separation is at a local minimum.
The caller may indicate that the region of interest
is the set of time intervals where the quantity is
within a specified measure of an absolute extremum.
The argument ADJUST (described below) is used to
specify this measure.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
The relate string lacks sensitivity to case, leading
and trailing blanks.
refval the double precision reference value used together with
relate argument to define an equality or inequality to
satisfy by the selected coordinate of the subpoint
vector. See the discussion of relate above for
further information.
The units of refval correspond to the type as defined
by coord, radians for angular measures, kilometers for
distance measures.
adjust a double precision value used to modify searches for
absolute extrema: when 'relate' is set to ABSMAX or ABSMIN and
'adjust' is set to a positive value, gfsubc_c finds times
when the position vector coordinate is within adjust
radians/kilometers of the specified extreme value.
For 'relate' set to ABSMAX, the result window contains
time intervals when the position vector coordinate has
values between ABSMAX - adjust and ABSMAX.
For 'relate' set to ABSMIN, the result window contains
time intervals when the position vector coordinate has
values between ABSMIN and ABSMIN + adjust.
'adjust' is not used for searches for local extrema,
equality or inequality conditions.
step the double precision time step size to use in the search.
step must be short enough for a search using this step
size to locate the time intervals where coordinate function
of the subpoint vector is monotone increasing or
decreasing. However, step must not be *too* short, or
the search will take an unreasonable amount of time.
The choice of step affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
step has units of TDB seconds.
nintvls an integer value specifying the number of intervals in the
the internal workspace array used by this routine. 'nintvls'
should be at least as large as the number of intervals
within the search region on which the specified observer-target
vector coordinate function is monotone increasing or decreasing.
It does no harm to pick a value of 'nintvls' larger than the
minimum required to execute the specified search, but if chosen
too small, the search will fail.
cnfine a double precision SPICE window that confines the time
period over which the specified search is conducted.
cnfine may consist of a single interval or a collection
of intervals.
In some cases the confinement window can be used to
greatly reduce the time period that must be searched
for the desired solution. See the Particulars section
below for further discussion.
See the Examples section below for a code example
that shows how to create a confinement window.
-Detailed_Output
cnfine is the input confinement window, updated if necessary
so the control area of its data array indicates the
window's size and cardinality. The window data are
unchanged.
result the SPICE window of intervals, contained within the
confinement window cnfine, on which the specified
constraint is satisfied.
If result is non-empty on input, its contents
will be discarded before gfsubc_c conducts its
search.
result must be declared and initialized with sufficient
size to capture the full set of time intervals
within the search region on which the specified constraint
is satisfied.
If the search is for local extrema, or for absolute
extrema with adjust set to zero, then normally each
interval of result will be a singleton: the left and
right endpoints of each interval will be identical.
If no times within the confinement window satisfy the
constraint, result will be returned with a
cardinality of zero.
-Parameters
SPICE_GF_CNVTOL
is the convergence tolerance used for finding endpoints
of the intervals comprising the result window.
SPICE_GF_CNVTOL is used to determine when binary searches
for roots should terminate: when a root is bracketed
within an interval of length SPICE_GF_CNVTOL; the root is
considered to have been found.
The accuracy, as opposed to precision, of roots found by
this routine depends on the accuracy of the input data.
In most cases, the accuracy of solutions will be inferior
to their precision.
SPICE_GF_CNVTOL has the value 1.0e-6. Units are TDB
seconds.
-Exceptions
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except
that if the step size is non-positive, an error is signaled
by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
wncond_c can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error will be diagnosed by a routine
in the call tree of this routine.
4) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
5) If the aberration correction specifier contains an
unrecognized value, an error is signaled by a routine in the
call tree of this routine.
6) If `adjust' is negative, an error is signaled by a routine in
the call tree of this routine.
7) If either of the input body names do not map to NAIF ID
codes, an error is signaled by a routine in the call tree of
this routine.
8) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
9) If any input string argument pointer is null, the error
SPICE(NULLPOINTER) will be signaled.
10) If any input string argument is empty, the error
SPICE(EMPTYSTRING) will be signaled.
11) If the workspace interval count 'nintvls' is less than 1, the
error SPICE(VALUEOUTOFRANGE) will be signaled.
12) If the required amount of workspace memory cannot be
allocated, the error SPICE(MALLOCFAILURE) will be
signaled.
-Files
Appropriate SPK and PCK kernels must be loaded by the
calling program before this routine is called.
The following data are required:
- SPK data: the calling application must load ephemeris data
for the targets, observer, and any intermediate objects in
a chain connecting the targets and observer that cover the time
period specified by the window CNFINE. If aberration
corrections are used, the states of target and observer
relative to the solar system barycenter must be calculable
from the available ephemeris data. Typically ephemeris data
are made available by loading one or more SPK files using
FURNSH.
- PCK data: bodies modeled as triaxial ellipsoids must have
semi-axis lengths provided by variables in the kernel pool.
Typically these data are made available by loading a text
PCK file using FURNSH.
- If non-inertial reference frames are used, then PCK
files, frame kernels, C-kernels, and SCLK kernels may be
needed.
Such kernel data are normally loaded once per program
run, NOT every time this routine is called.
-Particulars
This routine provides a simpler, but less flexible interface
than does the routine gfevnt_c for conducting searches for
subpoint position vector coordinate value events.
Applications that require support for progress reporting, interrupt
handling, non-default step or refinement functions, or non-default
convergence tolerance should call gfevnt_c rather than this routine.
This routine determines a set of one or more time intervals
within the confinement window when the selected coordinate of
the subpoint position vector satisfies a caller-specified
constraint. The resulting set of intervals is returned as a SPICE
window.
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the specified
coordinate function is monotone increasing and monotone
decreasing. Each of these time periods is represented by a SPICE
window. Having found these windows, all of the coordinate
function's local extrema within the confinement window are known.
Absolute extrema then can be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. Since the boundary
of the solution set for any inequality constraint is the set
of points where an equality constraint is met, the solutions of
both equality and inequality constraints can be found easily
once the monotone windows have been found.
Step Size
=========
The monotone windows (described above) are found using a two-step
search process. Each interval of the confinement window is
searched as follows: first, the input step size is used to
determine the time separation at which the sign of the rate of
change of coordinate will be sampled. Starting at
the left endpoint of an interval, samples will be taken at each
step. If a change of sign is found, a root has been bracketed; at
that point, the time at which the time derivative of the coordinate
is zero can be found by a refinement process, for example,
using a binary search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the coordinate function is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is shorter than the
shortest solution interval.
Having some knowledge of the relative geometry of the target and
observer can be a valuable aid in picking a reasonable step size.
In general, the user can compensate for lack of such knowledge by
picking a very short step size; the cost is increased computation
time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
As described above, the root-finding process used by this routine
involves first bracketing roots and then using a search process
to locate them. "Roots" are both times when local extrema are
attained and times when the distance function is equal to a
reference value. All endpoints of the intervals comprising the
result window are either endpoints of intervals of the
confinement window or roots.
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set by the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value in the f2c'd
routine so that the tolerance doesn't become the limiting factor
in the accuracy of solutions found by this routine. In general the
accuracy of input data will be the limiting factor.
To use a different tolerance value, a lower-level GF routine such
as gfevnt_c must be called. Making the tolerance tighter than
SPICE_GF_CNVTOL is unlikely to be useful, since the results are unlikely
to be more accurate. Making the tolerance looser will speed up
searches somewhat, since a few convergence steps will be omitted.
However, in most cases, the step size is likely to have a much
greater effect on processing time than would the convergence
tolerance.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed.
Practical use of the coordinate search capability would likely
consist of searches over multiple coordinate constraints to find
time intervals that satisfies the constraints. An effective
technique to accomplish such a search is to use the result
window from one search as the confinement window of the next.
Longitude and Right Ascension
=============================
The cyclic nature of the longitude and right ascension coordinates
produces branch cuts at +/- 180 degrees longitude and 0-360
longitude. Round-off error may cause solutions near these branches
to cross the branch. Use of the SPICE routine wncond_c will contract
solution windows by some epsilon, reducing the measure of the
windows and eliminating the branch crossing. A one millisecond
contraction will in most cases eliminate numerical round-off caused
branch crossings.
-Examples
The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
The example shown below requires a "standard" set of SPICE
kernels. We list these kernels in a meta kernel named 'standard.tm'.
KPL/MK
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de414.bsp Planetary ephemeris
pck00008.tpc Planet orientation and
radii
naif0008.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( '/kernels/gen/lsk/naif0008.tls'
'/kernels/gen/spk/de414.bsp'
'/kernels/gen/pck/pck00008.tpc'
)
Example:
Find the time during 2007 for which the subpoint position vector
of the sun on earth in the IAU_EARTH frame lies within a geodetic
latitude-longitude "box" defined as
16 degrees <= latitude <= 17 degrees
85 degrees <= longitude <= 86 degrees
This problem requires four searches, each search on one of the
box restrictions. The user needs also realize the temporal
behavior of latitude greatly differs from that of the longitude. The
sub-observer point latitude varies between approximately 23.44 degrees
and -23.44 degrees during the year. The sub-observer point longitude
varies between -180 degrees and 180 degrees in one day.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SpiceUsr.h"
#define MAXWIN 100
#define TIMFMT "YYYY-MON-DD HR:MN:SC.###### (TDB) ::TDB ::RND"
#define STRLEN 64
int main( int argc, char **argv )
{
/.
Create the needed windows. Note, one window
consists of two values, so the total number
of cell values to allocate equals twice
the number of intervals.
./
SPICEDOUBLE_CELL ( result1, 2*MAXWIN );
SPICEDOUBLE_CELL ( result2, 2*MAXWIN );
SPICEDOUBLE_CELL ( result3, 2*MAXWIN );
SPICEDOUBLE_CELL ( result4, 2*MAXWIN );
SPICEDOUBLE_CELL ( cnfine, 2 );
SpiceDouble begtim;
SpiceDouble endtim;
SpiceDouble step;
SpiceDouble adjust;
SpiceDouble refval;
SpiceDouble beg;
SpiceDouble end;
SpiceChar begstr [ STRLEN ];
SpiceChar endstr [ STRLEN ];
SpiceChar * target = "EARTH";
SpiceChar * obsrvr = "SUN";
SpiceChar * fixref = "IAU_EARTH";
SpiceChar * method = "Near point: ellipsoid";
SpiceChar * crdsys = "GEODETIC";
SpiceChar * abcorr = "NONE";
SpiceInt count;
SpiceInt i;
/.
Load kernels.
./
furnsh_c( "standard.tm" );
/.
Store the time bounds of our search interval in
the cnfine confinement window.
./
str2et_c( "2007 JAN 01", &begtim );
str2et_c( "2008 JAN 01", &endtim );
wninsd_c ( begtim, endtim, &cnfine );
/.
Perform four searches to determine the times when the
latitude-longitude box restriction conditions apply to
the subpoint vector.
Perform the searches such that the result window of a search
serves as the confinement window of the subsequent search.
Since the latitude coordinate varies slowly and is well behaved
over the time of the confinement window, search first for the
windows satisfying the latitude requirements, then use that result
as confinement for the longitude search.
./
/.
The latitude varies relatively slowly, ~46 degrees during the
year. The extrema occur approximately every six months.
Search using a step size less than half that value (180 days).
For this example use ninety days (in units of seconds).
./
step = (90.)*spd_c();
adjust = 0.;
{
SpiceChar * coord = "LATITUDE";
SpiceChar * relate = ">";
refval = 16. *rpd_c();
gfsubc_c ( target, fixref,
method, abcorr, obsrvr,
crdsys, coord,
relate, refval,
adjust, step,
MAXWIN,
&cnfine, &result1 );
}
{
SpiceChar * coord = "LATITUDE";
SpiceChar * relate = "<";
refval = 17. *rpd_c();
gfsubc_c ( target, fixref,
method, abcorr, obsrvr,
crdsys, coord,
relate, refval,
adjust, step,
MAXWIN,
&result1, &result2 );
}
/.
Now the longitude search.
./
/.
Reset the stepsize to something appropriate for the 360
degrees in 24 hours domain. The longitude shows near
linear behavior so use a stepsize less than half the period
of twelve hours. Ten hours will suffice in this case.
./
step = (10./24.)*spd_c();
{
SpiceChar * coord = "LONGITUDE";
SpiceChar * relate = ">";
refval = 85. *rpd_c();
gfsubc_c ( target, fixref,
method, abcorr, obsrvr,
crdsys, coord,
relate, refval,
adjust, step,
MAXWIN,
&result2, &result3 );
/.
Contract the endpoints of each window to account
for possible round-off error at the -180/180 degree branch.
A contraction value of a millisecond should eliminate
any round-off caused branch crossing.
./
wncond_c( 1e-3, 1e-3, &result3 );
}
{
SpiceChar * coord = "LONGITUDE";
SpiceChar * relate = "<";
refval = 86. *rpd_c();
gfsubc_c ( target, fixref,
method, abcorr, obsrvr,
crdsys, coord,
relate, refval,
adjust, step,
MAXWIN,
&result3, &result4 );
}
/.
List the beginning and ending points in each interval
if result contains data.
./
count = wncard_c( &result4 );
/.
Display the results.
./
if (count == 0 )
{
printf ( "Result window is empty.\n\n" );
}
else
{
for ( i = 0; i < count; i++ )
{
/.
Fetch the endpoints of the Ith interval
of the result window.
./
wnfetd_c ( &result4, i, &beg, &end );
timout_c ( beg, TIMFMT, STRLEN, begstr );
timout_c ( end, TIMFMT, STRLEN, endstr );
printf ( "Interval %d\n", i + 1);
printf ( "Beginning TDB %s \n", begstr );
printf ( "Ending TDB %s \n\n", endstr );
}
}
kclear_c();
return( 0 );
}
The program outputs:
Interval 1
Beginning TDB 2007-MAY-05 06:14:04.637735 (TDB)
Ending TDB 2007-MAY-05 06:18:04.621908 (TDB)
Interval 2
Beginning TDB 2007-MAY-06 06:13:59.583483 (TDB)
Ending TDB 2007-MAY-06 06:17:59.569239 (TDB)
Interval 3
Beginning TDB 2007-MAY-07 06:13:55.102939 (TDB)
Ending TDB 2007-MAY-07 06:17:55.090299 (TDB)
Interval 4
Beginning TDB 2007-MAY-08 06:13:51.202604 (TDB)
Ending TDB 2007-MAY-08 06:17:51.191583 (TDB)
Interval 5
Beginning TDB 2007-AUG-06 06:23:17.282927 (TDB)
Ending TDB 2007-AUG-06 06:27:17.264009 (TDB)
Interval 6
Beginning TDB 2007-AUG-07 06:23:10.545441 (TDB)
Ending TDB 2007-AUG-07 06:27:10.524926 (TDB)
Interval 7
Beginning TDB 2007-AUG-08 06:23:03.233996 (TDB)
Ending TDB 2007-AUG-08 06:27:03.211889 (TDB)
-Restrictions
1) The kernel files to be used by this routine must be loaded
(normally via the CSPICE routine furnsh_c) before this routine
is called.
2) This routine has the side effect of re-initializing the
coordinate quantity utility package. Callers may
need to re-initialize the package after calling this routine.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
E.D. Wright (JPL)
-Version
-CSPICE Version 1.0.1, 26-AUG-2009, EDW (JPL)
Edit to Example description, replaced "intercept" with
"sub-observer point."
Correction of several typos.
-CSPICE Version 1.0.0, 10-FEB-2009 (NJB) (EDW)
-Index_Entries
GF subpoint coordinate search
-&
*/
{ /* Begin gfsubc_c */
/*
Local variables
*/
doublereal * work;
SpiceInt nBytes;
static SpiceInt nw = SPICE_GF_NWMAX;
/*
Participate in error tracing.
*/
if ( return_c() )
{
return;
}
chkin_c ( "gfsubc_c" );
/*
Make sure cell data types are d.p.
*/
CELLTYPECHK2 ( CHK_STANDARD, "gfsubc_c", SPICE_DP, cnfine, result );
/*
Initialize the input cells if necessary.
*/
CELLINIT2 ( cnfine, result );
/*
Check the input strings to make sure each pointer is non-null
and each string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "gfsubc_c", target );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", fixref );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", method );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", abcorr );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", obsrvr );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", crdsys );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", coord );
CHKFSTR ( CHK_STANDARD, "gfsubc_c", relate );
/*
Check the workspace size; some mallocs have a violent
dislike for negative allocation amounts. To be safe,
rule out a count of zero intervals as well.
*/
if ( nintvls < 1 )
{
setmsg_c ( "The specified workspace interval count # was "
"less than the minimum allowed value of one (1)." );
errint_c ( "#", nintvls );
sigerr_c ( "SPICE(VALUEOUTOFRANGE)" );
chkout_c ( "gfposc_c" );
return;
}
/*
Allocate the workspace. 'nintvls' indicates the maximum number of
intervals returned in 'result'. An interval consists of
two values.
*/
nintvls = 2 * nintvls;
nBytes = ( nintvls + SPICE_CELL_CTRLSZ ) * nw * sizeof(SpiceDouble);
work = (doublereal *) alloc_SpiceMemory( nBytes );
if ( !work )
{
setmsg_c ( "Workspace allocation of # bytes failed due to "
"malloc failure" );
errint_c ( "#", nBytes );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "gfsubc_c" );
return;
}
/*
Let the f2'd routine do the work.
*/
gfsubc_ ( ( char * ) target,
( char * ) fixref,
( char * ) method,
( char * ) abcorr,
( char * ) obsrvr,
( char * ) crdsys,
( char * ) coord,
( char * ) relate,
( doublereal * ) &refval,
( doublereal * ) &adjust,
( doublereal * ) &step,
( doublereal * ) (cnfine->base),
( integer * ) &nintvls,
( integer * ) &nw,
( doublereal * ) work,
( doublereal * ) (result->base),
( ftnlen ) strlen(target),
( ftnlen ) strlen(fixref),
( ftnlen ) strlen(method),
( ftnlen ) strlen(abcorr),
( ftnlen ) strlen(obsrvr),
( ftnlen ) strlen(crdsys),
( ftnlen ) strlen(coord),
( ftnlen ) strlen(relate) );
/*
De-allocate the workspace.
*/
free_SpiceMemory( work );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, result ) ;
}
ALLOC_CHECK;
chkout_c ( "gfsubc_c" );
} /* End gfsubc_c */
void reordl_c ( ConstSpiceInt * iorder,
SpiceInt ndim,
SpiceBoolean * array )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
iorder I Order vector to be used to re-order array.
ndim I Dimension of array.
array I/O Array to be re-ordered.
-Detailed_Input
iorder is the order vector to be used to re-order the input
array. The first element of iorder is the index of
the first item of the re-ordered array, and so on.
Note that the order imposed by reordl_c is not the
same order that would be imposed by a sorting
routine. In general, the order vector will have
been created (by one of the order routines) for
a related array, as illustrated in the example below.
The elements of iorder range from zero to ndim-1.
ndim is the number of elements in the input array.
array on input, is an array containing some number of
elements in unspecified order.
-Detailed_Output
array on output, is the same array, with the elements
in re-ordered as specified by iorder.
-Parameters
None.
-Exceptions
1) If memory cannot be allocated to create a Fortran-style version of
the input order vector, the error SPICE(MALLOCFAILED) is signaled.
2) If memory cannot be allocated to create a type "logical" copy of the
the input SpiceBoolean array, the error SPICE(MALLOCFAILED) is
signaled.
3) If ndim < 2, this routine executes a no-op. This case is
not an error.
-Files
None.
-Particulars
reordl_c uses a cyclical algorithm to re-order the elements of
the array in place. After re-ordering, element iorder[0] of
the input array is the first element of the output array,
element iorder[1] is the input array is the second element of
the output array, and so on.
The order vector used by reordl_c is typically created for
a related array by one of the order*_c routines, as shown in
the example below.
-Examples
In the following example, the order*_c and reord*_c routines are
used to sort four related arrays (containing the names,
masses, integer ID codes, and visual magnitudes for a group
of satellites). This is representative of the typical use of
these routines.
#include "SpiceUsr.h"
.
.
.
/.
Sort the object arrays by name.
./
orderc_c ( namlen, names, n, iorder );
ordvec
reordc_c ( iorder, n, namlen, names );
reordd_c ( iorder, n, masses );
reordi_c ( iorder, n, codes );
reordd_c ( iorder, n, vmags );
-Restrictions
None.
-Author_and_Institution
N.J. Bachman (JPL)
W.L. Taber (JPL)
I.M. Underwood (JPL)
-Literature_References
None.
-Version
-CSPICE Version 1.0.0, 10-JUL-2002 (NJB) (WLT) (IMU)
-Index_Entries
reorder a logical array
-&
*/
{ /* Begin reordl_c */
/*
Local variables
*/
logical * lArray;
SpiceInt aSize;
SpiceInt i ;
SpiceInt * ordvec;
SpiceInt vSize;
/*
If the input array doesn't have at least two elements, return
immediately.
*/
if ( ndim < 2 )
{
return;
}
/*
Get a local copy of the input order vector; map the vector's contents
to the range 1:ndim.
*/
vSize = ndim * sizeof(SpiceInt);
ordvec = (SpiceInt *) malloc( vSize );
if ( ordvec == 0 )
{
chkin_c ( "reordl_c" );
setmsg_c ( "Failure on malloc call to create array "
"for Fortran-style order vector. Tried "
"to allocate # bytes." );
errint_c ( "#", vSize );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "reordl_c" );
return;
}
for ( i = 0; i < ndim; i++ )
{
ordvec[i] = iorder[i] + 1;
}
/*
Get a local copy of the input logical array; use type logical
to ensure compatibility with code translated by f2c.
*/
aSize = ndim * sizeof(logical);
lArray = (logical *) malloc( aSize );
if ( lArray == 0 )
{
free ( ordvec );
chkin_c ( "reordl_c" );
setmsg_c ( "Failure on malloc call to create array "
"for Fortran-style order vector. Tried "
"to allocate # bytes." );
errint_c ( "#", aSize );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "reordl_c" );
return;
}
for ( i = 0; i < ndim; i++ )
{
lArray[i] = array[i];
}
reordl_ ( ( integer * ) ordvec,
( integer * ) &ndim,
( logical * ) lArray );
/*
Write the re-ordered result to the output array.
*/
for ( i = 0; i < ndim; i++ )
{
array[i] = (SpiceBoolean) lArray[i];
}
free ( ordvec );
free ( lArray );
} /* End reordl_c */
void dasac_c ( SpiceInt handle,
SpiceInt n,
SpiceInt buflen,
const void * buffer )
/*
-Brief_I/O
Variable I/O Description
-------- --- --------------------------------------------------
handle I DAS handle of a file opened with write access.
n I Number of comments to put into the comment area.
buflen I Line length associated with buffer.
buffer I Buffer of lines to be put into the comment area.
-Detailed_Input
handle The file handle of a binary DAS file which has been
opened with write access.
n The number of strings in buffer that are to be
appended to the comment area of the binary DAS file
attached to handle.
buflen is the common length of the strings in buffer, including the
terminating nulls.
buffer A buffer containing comments which are to be added
to the comment area of the binary DAS file attached
to handle. buffer should be declared as follows:
ConstSpiceChar buffer [n][buflen]
Each string in buffer is null-terminated.
-Detailed_Output
None.
-Parameters
None.
-Exceptions
1) If the number of comments to be added is not positive, the
error SPICE(INVALIDARGUMENT) will be signaled.
2) If a non-null, non printing ASCII character is encountered in the
comments, the error SPICE(ILLEGALCHARACTER) will be
signaled.
3) If the binary DAS file attached to handle is not open for
write access, an error will be signaled by a routine called
by this routine.
4) If the input buffer pointer is null, the error SPICE(NULLPOINTER)
will be signaled.
5) If the input buffer string length buflen is not at least 2,
the error SPICE(STRINGTOOSHORT) will be signaled.
-Files
See argument handle in Detailed_Input.
-Particulars
Binary DAS files contain a data area which is reserved for storing
annotations or descriptive textual information about the data
contained in a file. This area is referred to as the "comment
area" of the file. The comment area of a DAS file is a line
oriented medium for storing textual information. The comment
area preserves any leading or embedded white space in the line(s)
of text which are stored so that the appearance of the
information will be unchanged when it is retrieved (extracted) at
some other time. Trailing blanks, however, are NOT preserved,
due to the way that character strings are represented in
standard Fortran 77.
This routine will take a buffer of text lines and add (append)
them to the comment area of a binary DAS file. If there are no
comments in the comment area of the file, then space will be
allocated and the text lines in buffer will then placed into the
comment area. The text lines may contain only printable ASCII
characters (decimal values 32 - 126).
There is no maximum length imposed on the significant portion
of a text line that may be placed into the comment area of a
DAS file. The maximum length of a line stored in the comment
area should be reasonable, however, so that they may be easily
extracted. A good value for this would be 255 characters, as
this can easily accommodate "screen width" lines as well as
long lines which may contain some other form of information.
-Examples
Let
handle be the handle for a DAS file which has been opened
with write access.
n be the number of lines of text to be added to the
comment area of the binary DAS file attached to
handle.
BUFLEN be the declared line length of the buffer.
buffer is a list of text lines to be added to the comment
area of the binary DAS file attached to handle.
The call
dasac_c ( handle, n, BUFLEN, buffer );
will append the first n line(s) in buffer to the comment area
of the binary DAS file attached to handle.
-Restrictions
1) This routine uses constants that are specific to the ASCII
character sequence. The results of using this routine with
a different character sequence are unpredictable.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
K.R. Gehringer (JPL)
-Version
-CSPICE Version 1.1.0, 02-MAR-2003 (NJB)
Added error check in wrapper for non-positive
buffer line count.
-CSPICE Version 1.0.0, 25-FEB-2003 (NJB) (KRG)
-Index_Entries
add comments to a binary das file
append comments to a das file comment area
-&
*/
{ /* Begin dasac_c */
/*
Local variables
*/
SpiceChar * fCvalsArr;
SpiceInt fCvalsLen;
/*
Participate in error tracing.
*/
if ( return_c() )
{
return;
}
chkin_c ( "dasac_c" );
/*
Check the line count of the input buffer.
*/
if ( n < 1 )
{
setmsg_c ( "Comment buffer line count n = #; must be positive." );
errint_c ( "#", n );
sigerr_c ( "SPICE(INVALIDARGUMENT)" );
chkout_c ( "dasac_c" );
return;
}
/*
Check the input buffer for null pointer or short lines.
*/
CHKOSTR ( CHK_STANDARD, "dasac_c", buffer, buflen );
/*
Map the input buffer to a Fortran-style buffer.
*/
C2F_MapStrArr ( "dasac_c", n, buflen, buffer, &fCvalsLen, &fCvalsArr );
if ( failed_c() )
{
chkout_c ( "dasac_c" );
return;
}
/*
Call the f2c'd routine.
*/
dasac_ ( ( integer * ) &handle,
( integer * ) &n,
( char * ) fCvalsArr,
( ftnlen ) fCvalsLen );
/*
Free the dynamically allocated array.
*/
free ( fCvalsArr );
chkout_c ( "dasac_c" );
} /* End dasac_c */
void gfposc_c ( ConstSpiceChar * target,
ConstSpiceChar * frame,
ConstSpiceChar * abcorr,
ConstSpiceChar * obsrvr,
ConstSpiceChar * crdsys,
ConstSpiceChar * coord,
ConstSpiceChar * relate,
SpiceDouble refval,
SpiceDouble adjust,
SpiceDouble step,
SpiceInt nintvls,
SpiceCell * cnfine,
SpiceCell * result )
/*
-Brief_I/O
Variable I/O Description
-------- --- --------------------------------------------------
SPICE_GF_CNVTOL
P Convergence tolerance.
target I Name of the target body
frame I Name of the reference frame for coordinate calculations
abcorr I Aberration correction flag
obsrvr I Name of the observing body
crdsys I Name of the coordinate system containing COORD
coord I Name of the coordinate of interest
relate I Operator that either looks for an extreme value
(max, min, local, absolute) or compares the
coordinate value and refval
refval I Reference value
adjust I Adjustment value for absolute extrema searches
step I Step size used for locating extrema and roots
nintvls I Workspace window interval count
cnfine I-O SPICE window to which the search is restricted
result O SPICE window containing results
-Detailed_Input
target the string name of a target body. Optionally, you may
supply the integer ID code for the object as an
integer string. For example both 'MOON' and '301'
are legitimate strings that indicate the moon is the
target body.
The target and observer define a position vector
that points from the observer to the target.
frame the string name of the reference frame in which to perform
state look-ups and coordinate calculations.
The SPICE frame subsystem must recognize the 'frame' name.
abcorr the string description of the aberration corrections to apply
to the state evaluations to account for one-way light time
and stellar aberration.
This routine accepts the same aberration corrections as does
the SPICE routine SPKEZR. See the header of SPKEZR for a
detailed description of the aberration correction options.
For convenience, the options are listed below:
'NONE' Apply no correction.
'LT' "Reception" case: correct for
one-way light time using a Newtonian
formulation.
'LT+S' "Reception" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
'CN' "Reception" case: converged
Newtonian light time correction.
'CN+S' "Reception" case: converged
Newtonian light time and stellar
aberration corrections.
'XLT' "Transmission" case: correct for
one-way light time using a Newtonian
formulation.
'XLT+S' "Transmission" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
'XCN' "Transmission" case: converged
Newtonian light time correction.
'XCN+S' "Transmission" case: converged
Newtonian light time and stellar
aberration corrections.
The abcorr string lacks sensitivity to case, and to embedded,
leading and trailing blanks.
obsrvr the string naming the observing body. Optionally, you
may supply the ID code of the object as an integer
string. For example, both 'EARTH' and '399' are
legitimate strings to supply to indicate the
observer is Earth.
crdsys the string name of the coordinate system for which the
coordinate of interest is a member.
coord the string name of the coordinate of interest in crdsys.
The supported coordinate systems and coordinate names are:
Coordinate System (CRDSYS) Coordinates (COORD) Range
'RECTANGULAR' 'X'
'Y'
'Z'
'LATITUDINAL' 'RADIUS'
'LONGITUDE' (-Pi,Pi]
'LATITUDE' [-Pi/2,Pi/2]
'RA/DEC' 'RANGE'
'RIGHT ASCENSION' [0,2Pi)
'DECLINATION' [-Pi/2,Pi/2]
'SPHERICAL' 'RADIUS'
'COLATITUDE' [0,Pi]
'LONGITUDE' (-Pi,Pi]
'CYLINDRICAL' 'RADIUS'
'LONGITUDE' [0,2Pi)
'Z'
'GEODETIC' 'LONGITUDE' (-Pi,Pi]
'LATITUDE' [-Pi/2,Pi/2]
'ALTITUDE'
'PLANETOGRAPHIC' 'LONGITUDE' [0,2Pi)
'LATITUDE' [-Pi/2,Pi/2]
'ALTITUDE'
Limit searches for coordinate events in the GEODETIC and
PLANETOGRAPHIC coordinate systems to TARGET bodies with
axial symmetry in the equatorial plane, i.e. equality
of the body X and Y radii (oblate or prolate spheroids).
relate the string or character describing the relational operator
used to define a constraint on the selected coordinate of the
observer-target vector. The result window found by this routine
indicates the time intervals where the constraint is satisfied.
Supported values of relate and corresponding meanings are
shown below:
'>' Separation is greater than the reference
value refval.
'=' Separation is equal to the reference
value refval.
'<' Separation is less than the reference
value refval.
'ABSMAX' Separation is at an absolute maximum.
'ABSMIN' Separation is at an absolute minimum.
'LOCMAX' Separation is at a local maximum.
'LOCMIN' Separation is at a local minimum.
The caller may indicate that the region of interest
is the set of time intervals where the quantity is
within a specified measure of an absolute extremum.
The argument ADJUST (described below) is used to
specify this measure.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
The relate string lacks sensitivity to case, leading
and trailing blanks.
refval the double precision reference value used together with
relate argument to define an equality or inequality to
satisfy by the selected coordinate of the observer-target
vector. See the discussion of relate above for
further information.
The units of refval correspond to the type as defined
by coord, radians for angular measures, kilometers for
distance measures.
adjust a double precision value used to modify searches for
absolute extrema: when relate is set to ABSMAX or ABSMIN and
adjust is set to a positive value, gfposc_c finds times when the
observer-target vector coordinate is within adjust
radians/kilometers of the specified extreme value.
For relate set to ABSMAX, the result window contains
time intervals when the observer-target vector coordinate has
values between ABSMAX - adjust and ABSMAX.
For relate set to ABSMIN, the result window contains
time intervals when the observer-target vector coordinate has
values between ABSMIN and ABSMIN + adjust.
adjust is not used for searches for local extrema,
equality or inequality conditions.
step the double precision time step size to use in the search.
step must be short enough for a search using this step
size to locate the time intervals where coordinate function
of the observer-target vector is monotone increasing or
decreasing. However, step must not be *too* short, or
the search will take an unreasonable amount of time.
The choice of step affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
step has units of seconds.
nintvls an integer value specifying the number of intervals in the
the internal workspace array used by this routine. 'nintvls'
should be at least as large as the number of intervals
within the search region on which the specified observer-target
vector coordinate function is monotone increasing or decreasing.
It does no harm to pick a value of 'nintvls' larger than the
minimum required to execute the specified search, but if chosen
too small, the search will fail.
cnfine a double precision SPICE window that confines the time
period over which the specified search is conducted.
cnfine may consist of a single interval or a collection
of intervals.
In some cases the confinement window can be used to
greatly reduce the time period that must be searched
for the desired solution. See the Particulars section
below for further discussion.
See the Examples section below for a code example
that shows how to create a confinement window.
-Detailed_Output
cnfine is the input confinement window, updated if necessary
so the control area of its data array indicates the
window's size and cardinality. The window data are
unchanged.
result the SPICE window of intervals, contained within the
confinement window cnfine, on which the specified
constraint is satisfied.
If result is non-empty on input, its contents
will be discarded before gfposc_c conducts its
search.
result must be declared and initialized with sufficient
size to capture the full set of time intervals
within the search region on which the specified constraint
is satisfied.
If the search is for local extrema, or for absolute
extrema with adjust set to zero, then normally each
interval of result will be a singleton: the left and
right endpoints of each interval will be identical.
If no times within the confinement window satisfy the
constraint, result will be returned with a
cardinality of zero.
-Parameters
SPICE_GF_CNVTOL
is the convergence tolerance used for finding endpoints
of the intervals comprising the result window.
SPICE_GF_CNVTOL is used to determine when binary searches
for roots should terminate: when a root is bracketed
within an interval of length SPICE_GF_CNVTOL; the root is
considered to have been found.
The accuracy, as opposed to precision, of roots found by
this routine depends on the accuracy of the input data.
In most cases, the accuracy of solutions will be inferior
to their precision.
SPICE_GF_CNVTOL has the value 1.0e-6. Units are TDB
seconds.
-Exceptions
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except
that if the step size is non-positive, an error is signaled
by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
wncond_c can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error will be diagnosed by a routine
in the call tree of this routine.
4) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
5) If the aberration correction specifier contains an
unrecognized value, an error is signaled by a routine in the
call tree of this routine.
6) If `adjust' is negative, an error is signaled by a routine in
the call tree of this routine.
7) If either of the input body names do not map to NAIF ID
codes, an error is signaled by a routine in the call tree of
this routine.
8) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
9) If any input string argument pointer is null, the error
SPICE(NULLPOINTER) will be signaled.
10) If any input string argument is empty, the error
SPICE(EMPTYSTRING) will be signaled.
11) If the workspace interval count 'nintvls' is less than 1, the
error SPICE(VALUEOUTOFRANGE) will be signaled.
12) If the required amount of workspace memory cannot be
allocated, the error SPICE(MALLOCFAILURE) will be
signaled.
-Files
Appropriate SPK and PCK kernels must be loaded by the
calling program before this routine is called.
The following data are required:
- SPK data: the calling application must load ephemeris data
for the targets, observer, and any intermediate objects in
a chain connecting the targets and observer that cover the time
period specified by the window CNFINE. If aberration
corrections are used, the states of target and observer
relative to the solar system barycenter must be calculable
from the available ephemeris data. Typically ephemeris data
are made available by loading one or more SPK files using
FURNSH.
- PCK data: bodies modeled as triaxial ellipsoids must have
semi-axis lengths provided by variables in the kernel pool.
Typically these data are made available by loading a text
PCK file using FURNSH.
- If non-inertial reference frames are used, then PCK
files, frame kernels, C-kernels, and SCLK kernels may be
needed.
Such kernel data are normally loaded once per program
run, NOT every time this routine is called.
-Particulars
This routine provides a simpler, but less flexible interface
than does the routine gfevnt_c for conducting searches for
observer-target vector coordinate value events. Applications
that require support for progress reporting, interrupt
handling, non-default step or refinement functions, or non-default
convergence tolerance should call gfevnt_c rather than this routine.
This routine determines a set of one or more time intervals
within the confinement window when the selected coordinate of
the observer-target vector satisfies a caller-specified
constraint. The resulting set of intervals is returned as a SPICE
window.
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the specified
coordinate function is monotone increasing and monotone
decreasing. Each of these time periods is represented by a SPICE
window. Having found these windows, all of the coordinate
function's local extrema within the confinement window are known.
Absolute extrema then can be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. Since the boundary
of the solution set for any inequality constraint is the set
of points where an equality constraint is met, the solutions of
both equality and inequality constraints can be found easily
once the monotone windows have been found.
Step Size
=========
The monotone windows (described above) are found using a two-step
search process. Each interval of the confinement window is
searched as follows: first, the input step size is used to
determine the time separation at which the sign of the rate of
change of coordinate will be sampled. Starting at
the left endpoint of an interval, samples will be taken at each
step. If a change of sign is found, a root has been bracketed; at
that point, the time at which the time derivative of the coordinate
is zero can be found by a refinement process, for example,
using a binary search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the coordinate function is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is shorter than the
shortest solution interval.
Having some knowledge of the relative geometry of the target and
observer can be a valuable aid in picking a reasonable step size.
In general, the user can compensate for lack of such knowledge by
picking a very short step size; the cost is increased computation
time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
As described above, the root-finding process used by this routine
involves first bracketing roots and then using a search process
to locate them. "Roots" are both times when local extrema are
attained and times when the distance function is equal to a
reference value. All endpoints of the intervals comprising the
result window are either endpoints of intervals of the
confinement window or roots.
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set by the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value in the f2c'd
routine so that the tolerance doesn't become the limiting factor
in the accuracy of solutions found by this routine. In general the
accuracy of input data will be the limiting factor.
To use a different tolerance value, a lower-level GF routine such
as gfevnt_c must be called. Making the tolerance tighter than
SPICE_GF_CNVTOL is unlikely to be useful, since the results are unlikely
to be more accurate. Making the tolerance looser will speed up
searches somewhat, since a few convergence steps will be omitted.
However, in most cases, the step size is likely to have a much
greater effect on processing time than would the convergence
tolerance.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed.
Practical use of the coordinate search capability would likely
consist of searches over multiple coordinate constraints to find
time intervals that satisfies the constraints. An effective
technique to accomplish such a search is to use the result
window from one search as the confinement window of the next.
Longitude and Right Ascension
=============================
The cyclic nature of the longitude and right ascension coordinates
produces branch cuts at +/- 180 degrees longitude and 0-360
longitude. Round-off error may cause solutions near these branches
to cross the branch. Use of the SPICE routine wncond_c will contract
solution windows by some epsilon, reducing the measure of the
windows and eliminating the branch crossing. A one millisecond
contraction will in most cases eliminate numerical round-off caused
branch crossings.
-Examples
The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
The examples shown below require a "standard" set of SPICE
kernels. We list these kernels in a meta kernel named 'standard.tm'.
KPL/MK
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de414.bsp Planetary ephemeris
pck00008.tpc Planet orientation and radii
naif0009.tls Leapseconds kernel
earthstns_itrf93_050714.bsp SPK for DSN Station Locations
earth_topo_050714.tf Topocentric DSN stations frame
definitions
earth_000101_080120_071029.bpc High precision earth PCK
\begindata
KERNELS_TO_LOAD = (
'/kernels/gen/lsk/naif0008.tls'
'/kernels/gen/spk/de414.bsp'
'/kernels/gen/pck/pck00008.tpc'
'/kernels/gen/spk/earthstns_itrf93_050714.bsp',
'/kernels/gen/fk/earth_topo_050714.tf',
'/kernels/gen/pck/earth_000101_080120_071029.bpc',
)
Example(1):
Find the time during 2007 for which the latitude of the
Earth-Sun vector in IAU_EARTH frame has the maximum value,
i.e. the latitude of the Tropic of Cancer.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SpiceUsr.h"
#define MAXWIN 750
#define TIMFMT "YYYY-MON-DD HR:MN:SC.###### (TDB) ::TDB ::RND"
#define TIMLEN 41
int main( int argc, char **argv )
{
/.
Create the needed windows. Note, one window
consists of two values, so the total number
of cell values to allocate is twice
the number of intervals.
./
SPICEDOUBLE_CELL ( result, 2*MAXWIN );
SPICEDOUBLE_CELL ( cnfine, 2 );
SpiceDouble begtim;
SpiceDouble endtim;
SpiceDouble step;
SpiceDouble adjust;
SpiceDouble refval;
SpiceDouble beg;
SpiceDouble end;
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
SpiceChar * relate = "ABSMAX";
SpiceChar * crdsys = "LATITUDINAL";
SpiceChar * coord = "LATITUDE";
SpiceChar * targ = "SUN";
SpiceChar * obsrvr = "EARTH";
SpiceChar * frame = "IAU_EARTH";
SpiceChar * abcorr = "NONE";
SpiceInt count;
SpiceInt i;
/.
Load kernels.
./
furnsh_c( "standard.tm" );
/.
Store the time bounds of our search interval in
the cnfine confinement window.
./
str2et_c( "2007 JAN 01", &begtim );
str2et_c( "2008 JAN 01", &endtim );
wninsd_c ( begtim, endtim, &cnfine );
/.
The latitude varies relatively slowly, ~46 degrees during the
year. The extrema occur approximately every six months.
Search using a step size less than half that value (180 days).
For this example use ninety days (in units of seconds).
./
step = (90.)*spd_c();
adjust = 0.;
refval = 0;
/.
List the beginning and ending points in each interval
if result contains data.
./
gfposc_c ( targ,
frame,
abcorr,
obsrvr,
crdsys,
coord,
relate,
refval,
adjust,
step,
MAXWIN,
&cnfine,
&result );
count = wncard_c( &result );
/.
Display the results.
./
if (count == 0 )
{
printf ( "Result window is empty.\n\n" );
}
else
{
for ( i = 0; i < count; i++ )
{
/.
Fetch the endpoints of the Ith interval
of the result window.
./
wnfetd_c ( &result, i, &beg, &end );
if ( beg == end )
{
timout_c ( beg, TIMFMT, TIMLEN, begstr );
printf ( "Event time: %s\n", begstr );
}
else
{
timout_c ( beg, TIMFMT, TIMLEN, begstr );
timout_c ( end, TIMFMT, TIMLEN, endstr );
printf ( "Interval %d\n", i + 1);
printf ( "From : %s \n", begstr );
printf ( "To : %s \n", endstr );
printf( " \n" );
}
}
}
kclear_c();
return( 0 );
}
The program outputs:
Event time: 2007-JUN-21 17:54:13.166910 (TDB)
Example(2):
A minor modification of the program listed in Example 1; find the
time during 2007 for which the latitude of the Earth-Sun vector
in IAU_EARTH frame has the minimum value, i.e. the latitude of
the Tropic of Capricorn.
Edit the example program, assign:
SpiceChar * relate = "ABSMIN";
The program outputs:
Event time: 2007-DEC-22 06:04:32.630160 (TDB)
Example(3):
Find the time during 2007 for which the Z component of the
Earth-Sun vector in IAU_EARTH frame has value 0, i.e. crosses
the equatorial plane (this also defines a zero latitude).
The search should return two times, one for an ascending
passage and one for descending.
Edit the example program, assign:
SpiceChar * relate = "=";
SpiceChar * crdsys = "RECTANGULAR";
SpiceChar * coord = "Z";
Note, this RELATE operator refers to the REFVAL value,
assigned to 0.D0 for this example.
The program outputs:
Event time: 2007-MAR-21 00:01:25.495120 (TDB)
Event time: 2007-SEP-23 09:46:39.574124 (TDB)
Example(4):
Find the times between Jan 1, 2007 and Jan 1, 2008 corresponding
to the apoapsis on the Moon's orbit around the Earth (note, the
GFDIST routine can also perform this search).
Edit the example program, assign:
This search requires a change in the step size since the Moon's
orbit about the earth (earth-moon barycenter) has a twenty-eight
day period. Use a step size something less than half that value.
In this case, we use twelve days.
SpiceChar * relate = "LOCMAX";
SpiceChar * crdsys = "SPHERICAL";
SpiceChar * coord = "RADIUS";
SpiceChar * targ = "MOON";
SpiceChar * frame = "J2000";
step = 12.*spd_c();
The program outputs:
Event time: 2007-JAN-10 16:26:18.805837 (TDB)
Event time: 2007-FEB-07 12:39:35.078525 (TDB)
Event time: 2007-MAR-07 03:38:07.334769 (TDB)
Event time: 2007-APR-03 08:38:55.222606 (TDB)
Event time: 2007-APR-30 10:56:49.847027 (TDB)
Event time: 2007-MAY-27 22:03:28.857783 (TDB)
Event time: 2007-JUN-24 14:26:23.639351 (TDB)
Event time: 2007-JUL-22 08:43:50.135565 (TDB)
Event time: 2007-AUG-19 03:28:33.538169 (TDB)
Event time: 2007-SEP-15 21:07:13.964698 (TDB)
Event time: 2007-OCT-13 09:52:30.819372 (TDB)
Event time: 2007-NOV-09 12:32:50.070555 (TDB)
Event time: 2007-DEC-06 16:54:31.225504 (TDB)
Example(5):
Find times between Jan 1, 2007 and Jan 1, 2008 when the latitude
(elevation) of the observer-target vector between DSS 17 and the
Moon, as observed in the DSS 17 topocentric (station) frame,
exceeds 83 degrees.
Edit the example program, assign:
This search uses a step size of four hours since the time
for all declination zero-to-max-to-zero passes within
the search window exceeds eight hours.
SpiceChar * relate = ">";
SpiceChar * crdsys = "LATITUDINAL";
SpiceChar * coord = "LATITUDE";
SpiceChar * targ = "MOON";
SpiceChar * obsrvr = "DSS-17";
SpiceChar * frame = "DSS-17_TOPO";
step = (4./24.)*spd_c();
refval = 83. * rpd_c();
The program outputs:
Interval 1
From : 2007-FEB-26 03:18:48.229806 (TDB)
To : 2007-FEB-26 03:31:29.734169 (TDB)
Interval 2
From : 2007-MAR-25 01:12:38.551183 (TDB)
To : 2007-MAR-25 01:23:53.908601 (TDB)
-Restrictions
1) The kernel files to be used by this routine must be loaded
(normally via the CSPICE routine furnsh_c) before this routine
is called.
2) This routine has the side effect of re-initializing the
coordinate quantity utility package. Callers may
need to re-initialize the package after calling this routine.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
E.D. Wright (JPL)
-Version
-CSPICE Version 1.0.1, 26-AUG-2009 (EDW)
Correction of several typos.
-CSPICE Version 1.0.0, 10-FEB-2009 (NJB) (EDW)
-Index_Entries
GF position coordinate search
-&
*/
{ /* Begin gfposc_c */
/*
Local variables
*/
doublereal * work;
SpiceInt nBytes;
static SpiceInt nw = SPICE_GF_NWMAX;
/*
Participate in error tracing.
*/
if ( return_c() )
{
return;
}
chkin_c ( "gfposc_c" );
/*
Make sure cell data types are d.p.
*/
CELLTYPECHK2 ( CHK_STANDARD, "gfposc_c", SPICE_DP, cnfine, result );
/*
Initialize the input cells if necessary.
*/
CELLINIT2 ( cnfine, result );
/*
Check the input strings to make sure each pointer is non-null
and each string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "gfposc_c", target );
CHKFSTR ( CHK_STANDARD, "gfposc_c", frame );
CHKFSTR ( CHK_STANDARD, "gfposc_c", abcorr );
CHKFSTR ( CHK_STANDARD, "gfposc_c", obsrvr );
CHKFSTR ( CHK_STANDARD, "gfposc_c", crdsys );
CHKFSTR ( CHK_STANDARD, "gfposc_c", coord );
CHKFSTR ( CHK_STANDARD, "gfposc_c", relate );
/*
Check the workspace size; some mallocs have a violent
dislike for negative allocation amounts. To be safe,
rule out a count of zero intervals as well.
*/
if ( nintvls < 1 )
{
setmsg_c ( "The specified workspace interval count # was "
"less than the minimum allowed value of one (1)." );
errint_c ( "#", nintvls );
sigerr_c ( "SPICE(VALUEOUTOFRANGE)" );
chkout_c ( "gfposc_c" );
return;
}
/*
Allocate the workspace. 'nintvls' indicates the maximum number of
intervals returned in 'result'. An interval consists of
two values.
*/
nintvls = 2 * nintvls;
nBytes = ( nintvls + SPICE_CELL_CTRLSZ ) * nw * sizeof(SpiceDouble);
work = (doublereal *) alloc_SpiceMemory( nBytes );
if ( !work )
{
setmsg_c ( "Workspace allocation of # bytes failed due to "
"malloc failure" );
errint_c ( "#", nBytes );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "gfposc_c" );
return;
}
/*
Let the f2'd routine do the work.
*/
gfposc_( ( char * ) target,
( char * ) frame,
( char * ) abcorr,
( char * ) obsrvr,
( char * ) crdsys,
( char * ) coord,
( char * ) relate,
( doublereal * ) &refval,
( doublereal * ) &adjust,
( doublereal * ) &step,
( doublereal * ) (cnfine->base),
( integer * ) &nintvls,
( integer * ) &nw,
( doublereal * ) work,
( doublereal * ) (result->base),
( ftnlen ) strlen(target),
( ftnlen ) strlen(frame),
( ftnlen ) strlen(abcorr),
( ftnlen ) strlen(obsrvr),
( ftnlen ) strlen(crdsys),
( ftnlen ) strlen(coord),
( ftnlen ) strlen(relate) );
/*
De-allocate the workspace.
*/
free_SpiceMemory( work );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, result ) ;
}
ALLOC_CHECK;
chkout_c ( "gfposc_c" );
} /* End gfposc_c */
void gfpa_c ( ConstSpiceChar * target,
ConstSpiceChar * illmn,
ConstSpiceChar * abcorr,
ConstSpiceChar * obsrvr,
ConstSpiceChar * relate,
SpiceDouble refval,
SpiceDouble adjust,
SpiceDouble step,
SpiceInt nintvls,
SpiceCell * cnfine,
SpiceCell * result )
/*
-Brief_I/O
Variable I/O Description
--------------- --- ------------------------------------------------
SPICE_GF_CNVTOL P Convergence tolerance
target I Name of the target body.
illmn I Name of the illuminating body.
abcorr I Aberration correction flag.
obsrvr I Name of the observing body.
relate I Relational operator.
refval I Reference value.
adjust I Adjustment value for absolute extrema searches.
step I Step size used for locating extrema and roots.
nintvls I Workspace window interval count.
cnfine I-O SPICE window to which the search is confined.
result O SPICE window containing results.
-Detailed_Input
target is the name of a target body. Optionally, you may supply
a string containing the integer ID code for the object.
For example both "MOON" and "301" are legitimate strings
that indicate the Moon is the target body.
Case and leading or trailing blanks are not significant
in the string `target'.
illmn the string name of the illuminating body. This will
normally be "SUN" but the algorithm can use any
ephemeris object
Case and leading or trailing blanks are not significant
in the string `illmn'.
abcorr indicates the aberration corrections to be applied to
the observer-target position vector to account for
one-way light time and stellar aberration.
Any aberration correction accepted by the SPICE
routine spkezr_c is accepted here. See the header
of spkezr_c for a detailed description of the
aberration correction options. For convenience,
the allowed aberation options are listed below:
"NONE" Apply no correction.
"LT" "Reception" case: correct for
one-way light time using a Newtonian
formulation.
"LT+S" "Reception" case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
"CN" "Reception" case: converged
Newtonian light time correction.
"CN+S" "Reception" case: converged
Newtonian light time and stellar
aberration corrections.
Note that this routine accepts only reception mode
aberration corrections.
Case and leading or trailing blanks are not significant
in the string `abcorr'.
obsrvr is the name of the observing body. Optionally, you may
supply a string containing the integer ID code for the
object. For example both "MOON" and "301" are legitimate
strings that indicate the Moon is the observer.
Case and leading or trailing blanks are not significant
in the string `obsrvr'.
relate is a relational operator used to define a constraint on
the phase angle. The result window found by
this routine indicates the time intervals where the
constraint is satisfied. Supported values of `relate'
and corresponding meanings are shown below:
">" The phase angle value is greater than the
reference value REFVAL.
"=" The phase angle value is equal to the
reference value REFVAL.
"<" The phase angle value is less than the
reference value REFVAL.
"ABSMAX" The phase angle value is at an absolute
maximum.
"ABSMIN" The phase angle value is at an absolute
minimum.
"LOCMAX" The phase angle value is at a local
maximum.
"LOCMIN" The phase angle value is at a local
minimum.
`relate' may be used to specify an "adjusted" absolute
extremum constraint: this requires the phase angle
to be within a specified offset relative to an
absolute extremum. The argument `adjust' (described
below) is used to specify this offset.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
Case and leading or trailing blanks are not significant
in the string `relate'.
`refval' is the reference value used together with the argument
`relate' to define an equality or inequality to be
satisfied by the phase angle. See the discussion of
`relate' above for further information.
The units of `refval' are radians.
adjust is a parameter used to modify searches for absolute
extrema: when `relate' is set to "ABSMAX" or "ABSMIN"
and `adjust' is set to a positive value, gfpa_c will
find times when the phase angle is within
`adjust' radians of the specified extreme value.
If `adjust' is non-zero and a search for an absolute
minimum `min' is performed, the result window contains
time intervals when the phase angle has values between
`min' and min+adjust.
If the search is for an absolute maximum `max', the
corresponding range is from max-adjust to `max'.
`adjust' is not used for searches for local extrema,
equality or inequality conditions.
step is the step size to be used in the search. `step' must
be shorter than any maximal time interval on which the
specified phase angle function is monotone increasing or
decreasing. That is, if the confinement window is
partitioned into alternating intervals on which the
phase angle function is either monotone increasing or
decreasing, `step' must be shorter than any of these
intervals.
However, `step' must not be *too* short, or the search
will take an unreasonable amount of time.
The choice of `step' affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
See the discussion of the parameter SPICE_GF_CNVTOL for
details.
STEP has units of TDB seconds.
nintvls is a parameter specifying the number of intervals that
can be accommodated by each of the dynamically allocated
workspace windows used internally by this routine.
In many cases, it's not necessary to compute an accurate
estimate of how many intervals are needed; rather, the
user can pick a size considerably larger than what's
really required.
However, since excessively large arrays can prevent
applications from compiling, linking, or running
properly, sometimes `nintvls' must be set according to
the actual workspace requirement. A rule of thumb for
the number of intervals needed is
nintvls = 2*n + ( m / step )
where
n is the number of intervals in the confinement
window
m is the measure of the confinement window, in
units of seconds
`step' is the search step size in seconds
cnfine is a SPICE window that confines the time period over
which the specified search is conducted. `cnfine' may
consist of a single interval or a collection of
intervals.
The endpoints of the time intervals comprising `cnfine'
are interpreted as seconds past J2000 TDB.
See the Examples section below for a code example that
shows how to create a confinement window.
-Detailed_Output
cnfine is the input confinement window, updated if necessary so
the control area of its data array indicates the
window's size and cardinality. The window data are
unchanged.
result is the window of intervals, contained within the
confinement window `cnfine', on which the specified
phase angle constraint is satisfied.
The endpoints of the time intervals comprising `result'
are interpreted as seconds past J2000 TDB.
If `result' is non-empty on input, its contents will be
discarded before gfpa_c conducts its search.
-Parameters
SPICE_GF_CNVTOL
is the convergence tolerance used for finding endpoints
of the intervals comprising the result window.
SPICE_GF_CNVTOL is used to determine when binary
searches for roots should terminate: when a root is
bracketed within an interval of length SPICE_GF_CNVTOL,
the root is considered to have been found.
The accuracy, as opposed to precision, of roots found by
this routine depends on the accuracy of the input data.
In most cases, the accuracy of solutions will be
inferior to their precision.
SPICE_GF_CNVTOL is declared in the header file
SpiceGF.h.
-Exceptions
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except
that if the step size is non-positive, an error is signaled
by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
wncond_c can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error will be diagnosed by a routine
in the call tree of this routine.
4) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
5) If the aberration correction specifier contains an
unrecognized value, an error is signaled by a routine in the
call tree of this routine.
6) If `adjust' is negative, an error is signaled by a routine in
the call tree of this routine.
7) If either of the input body names do not map to NAIF ID
codes, an error is signaled by a routine in the call tree of
this routine.
8) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
9) If the workspace interval count is less than 1, the error
SPICE(VALUEOUTOFRANGE) will be signaled.
10) If the required amount of workspace memory cannot be
allocated, the error SPICE(MALLOCFAILURE) will be
signaled.
11) If the output SPICE window `result' has insufficient capacity to
contain the number of intervals on which the specified geometric
condition is met, the error will be diagnosed by a routine in
the call tree of this routine. If the result window has size
less than 2, the error SPICE(INVALIDDIMENSION) will be signaled
by this routine.
12) If any input string argument pointer is null, the error
SPICE(NULLPOINTER) will be signaled.
13) If any input string argument is empty, the error
SPICE(EMPTYSTRING) will be signaled.
14) If either input cell has type other than SpiceDouble,
the error SPICE(TYPEMISMATCH) is signaled.
15) An error signals from a routine in the call tree of
this routine for any transmit mode aberration correction.
-Files
Appropriate SPK and PCK kernels must be loaded by the calling
program before this routine is called.
The following data are required:
- SPK data: the calling application must load ephemeris data
for the targets, observer, and any intermediate objects in
a chain connecting the targets and observer that cover the
time period specified by the window CNFINE. If aberration
corrections are used, the states of target and observer
relative to the solar system barycenter must be calculable
from the available ephemeris data. Typically ephemeris data
are made available by loading one or more SPK files using
furnsh_c.
Kernel data are normally loaded once per program run, NOT every
time this routine is called.
-Particulars
ILLMN OBS
ILLMN as seen * /
from TARG at | /
ET - LT. | /
>|..../< phase angle
| /
. | /
. | /
. * TARG as seen from OBS
SEP . TARG at ET
. /
/
*
This routine determines if the caller-specified constraint
condition on the geometric event (phase angle) is satisfied for
any time intervals within the confinement window `cnfine'. If one
or more such time intervals exist, those intervals are added
to the `result' window.
This routine provides a simpler, but less flexible interface
than does the routine gfevnt_c for conducting searches for
illuminator-target-observer phase angle value events.
Applications that require support for progress reporting,
interrupt handling, non-default step or refinement functions
should call gfevnt_c rather than this routine.
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the
phase angle function is monotone increasing and monotone
decreasing. Each of these time periods is represented by a SPICE
window. Having found these windows, all of the phase angle
function's local extrema within the confinement window are known.
Absolute extrema then can be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. Since the boundary
of the solution set for any inequality constraint is contained in
the union of
- the set of points where an equality constraint is met
- the boundary points of the confinement window
the solutions of both equality and inequality constraints can be
found easily once the monotone windows have been found.
Step Size
=========
The monotone windows (described above) are found using a two-step
search process. Each interval of the confinement window is
searched as follows: first, the input step size is used to
determine the time separation at which the sign of the rate of
change of phase angle will be sampled. Starting at
the left endpoint of an interval, samples will be taken at each
step. If a change of sign is found, a root has been bracketed; at
that point, the time at which the time derivative of the
phase angle is zero can be found by a refinement process, for
example, using a binary search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the phase angle function is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is longer than the
shortest solution interval.
Having some knowledge of the relative geometry of the target,
illumination source, and observer can be a valuable aid in
picking a reasonable step size. In general, the user can
compensate for lack of such knowledge by picking a very short
step size; the cost is increased computation time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
As described above, the root-finding process used by this routine
involves first bracketing roots and then using a search process to
locate them. "Roots" include times when extrema are attained and
times when the geometric quantity function is equal to a reference
value or adjusted extremum. All endpoints of the intervals comprising
the result window are either endpoints of intervals of the confinement
window or roots.
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set via the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value so that the
tolerance doesn't limit the accuracy of solutions found by this
routine. In general the accuracy of input data will be the limiting
factor.
The user may change the convergence tolerance from the default
SPICE_GF_CNVTOL value by calling the routine gfstol_c, e.g.
gfstol_c( tolerance value in seconds )
Call gfstol_c prior to calling this routine. All subsequent
searches will use the updated tolerance value.
Searches over time windows of long duration may require use of
larger tolerance values than the default: the tolerance must be
large enough so that it, when added to or subtracted from the
confinement window's lower and upper bounds, yields distinct time
values.
Setting the tolerance tighter than SPICE_GF_CNVTOL is unlikely to be
useful, since the results are unlikely to be more accurate.
Making the tolerance looser will speed up searches somewhat,
since a few convergence steps will be omitted. However, in most
cases, the step size is likely to have a much greater effect
on processing time than would the convergence tolerance.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed. See the "CASCADE"
example program in gf.req for a demonstration.
-Examples
The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: standard.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de421.bsp Planetary ephemeris
pck00009.tpc Planet orientation and
radii
naif0009.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'de421.bsp',
'pck00009.tpc',
'naif0009.tls' )
\begintext
Example:
Determine the time windows from December 1, 2006 UTC to
January 31, 2007 UTC for which the sun-moon-earth configuration
phase angle satisfies the relation conditions with respect to a
reference value of .57598845 radians (the phase angle at
January 1, 2007 00:00:00.000 UTC, 33.001707 degrees). Also
determine the time windows corresponding to the local maximum and
minimum phase angles, and the absolute maximum and minimum phase
angles during the search interval. The configuration defines the
sun as the illuminator, the moon as the target, and the earth as
the observer.
#include <stdio.h>
#include "SpiceUsr.h"
#define TIMFMT "YYYY MON DD HR:MN:SC.###"
#define NINTVL 5000
#define TIMLEN 41
#define NLOOPS 7
int main()
{
/.
Local variables
./
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
SPICEDOUBLE_CELL ( cnfine, 2 );
SPICEDOUBLE_CELL ( result, NINTVL*2 );
SpiceDouble adjust;
SpiceDouble et0;
SpiceDouble et1;
SpiceDouble phaseq;
SpiceDouble refval;
SpiceDouble start;
SpiceDouble step;
SpiceDouble stop;
SpiceInt i;
SpiceInt j;
/.
Define the values for target, observer, illuminator, and
aberration correction.
./
ConstSpiceChar * target = "moon";
ConstSpiceChar * illmn = "sun";
ConstSpiceChar * abcorr = "lt+s";
ConstSpiceChar * obsrvr = "earth";
ConstSpiceChar * relate [NLOOPS] = { "=",
"<",
">",
"LOCMIN",
"ABSMIN",
"LOCMAX",
"ABSMAX",
};
/.
Load kernels.
./
furnsh_c ( "standard.tm" );
/.
Store the time bounds of our search interval in
the confinement window.
./
str2et_c ( "2006 DEC 01", &et0 );
str2et_c ( "2007 JAN 31", &et1 );
wninsd_c ( et0, et1, &cnfine );
/.
Search using a step size of 1 day (in units of seconds).
The reference value is 0.57598845 radians. We're not using the
adjustment feature, so we set ADJUST to zero.
./
step = spd_c();
refval = 0.57598845;
adjust = 0.0;
for ( j = 0; j < NLOOPS; j++ )
{
printf ( "Relation condition: %s\n", relate[j] );
/.
Perform the search. The SPICE window `result' contains
the set of times when the condition is met.
./
gfpa_c ( target, illmn, abcorr, obsrvr,
relate[j], refval, adjust, step,
NINTVL, &cnfine, &result );
/.
Display the results.
./
if ( wncard_c(&result) == 0 )
{
printf ( "Result window is empty.\n\n" );
}
else
{
for ( i = 0; i < wncard_c(&result); i++ )
{
/.
Fetch the endpoints of the Ith interval
of the result window.
./
wnfetd_c ( &result, i, &start, &stop );
phaseq = phaseq_c ( start, target, illmn, obsrvr, abcorr );
timout_c ( start, TIMFMT, TIMLEN, begstr );
printf ( "Start time = %s %16.9f\n", begstr, phaseq );
phaseq = phaseq_c ( stop, target, illmn, obsrvr, abcorr );
timout_c ( stop, TIMFMT, TIMLEN, endstr );
printf ( "Stop time = %s %16.9f\n", endstr, phaseq );
}
printf("\n");
}
}
return ( 0 );
}
The program outputs:
Relation condition: =
Start time = 2006 DEC 02 13:31:34.414 0.575988450
Stop time = 2006 DEC 02 13:31:34.414 0.575988450
Start time = 2006 DEC 07 14:07:55.470 0.575988450
Stop time = 2006 DEC 07 14:07:55.470 0.575988450
Start time = 2006 DEC 31 23:59:59.997 0.575988450
Stop time = 2006 DEC 31 23:59:59.997 0.575988450
Start time = 2007 JAN 06 08:16:25.512 0.575988450
Stop time = 2007 JAN 06 08:16:25.512 0.575988450
Start time = 2007 JAN 30 11:41:32.557 0.575988450
Stop time = 2007 JAN 30 11:41:32.557 0.575988450
Relation condition: <
Start time = 2006 DEC 02 13:31:34.414 0.575988450
Stop time = 2006 DEC 07 14:07:55.470 0.575988450
Start time = 2006 DEC 31 23:59:59.997 0.575988450
Stop time = 2007 JAN 06 08:16:25.512 0.575988450
Start time = 2007 JAN 30 11:41:32.557 0.575988450
Stop time = 2007 JAN 31 00:00:00.000 0.468279091
Relation condition: >
Start time = 2006 DEC 01 00:00:00.000 0.940714974
Stop time = 2006 DEC 02 13:31:34.414 0.575988450
Start time = 2006 DEC 07 14:07:55.470 0.575988450
Stop time = 2006 DEC 31 23:59:59.997 0.575988450
Start time = 2007 JAN 06 08:16:25.512 0.575988450
Stop time = 2007 JAN 30 11:41:32.557 0.575988450
Relation condition: LOCMIN
Start time = 2006 DEC 05 00:16:50.317 0.086121423
Stop time = 2006 DEC 05 00:16:50.317 0.086121423
Start time = 2007 JAN 03 14:18:31.977 0.079899769
Stop time = 2007 JAN 03 14:18:31.977 0.079899769
Relation condition: ABSMIN
Start time = 2007 JAN 03 14:18:31.977 0.079899769
Stop time = 2007 JAN 03 14:18:31.977 0.079899769
Relation condition: LOCMAX
Start time = 2006 DEC 20 14:09:10.392 3.055062862
Stop time = 2006 DEC 20 14:09:10.392 3.055062862
Start time = 2007 JAN 19 04:27:54.600 3.074603891
Stop time = 2007 JAN 19 04:27:54.600 3.074603891
Relation condition: ABSMAX
Start time = 2007 JAN 19 04:27:54.600 3.074603891
Stop time = 2007 JAN 19 04:27:54.600 3.074603891
-Restrictions
1) The kernel files to be used by this routine must be loaded
(normally using the CSPICE routine furnsh_c) before this
routine is called.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
E.D. Wright (JPL)
-Version
-CSPICE Version 1.0.0, 15-JUL-2014 (EDW) (NJB)
-Index_Entries
GF phase angle search
-&
*/
{ /* Begin gfpa_c */
/*
Static local variables
*/
static SpiceInt nw = SPICE_GF_NWPA;
/*
Local variables
*/
doublereal * work;
SpiceInt nBytes;
/*
Participate in error tracing.
*/
if ( return_c() )
{
return;
}
chkin_c ( "gfpa_c" );
/*
Make sure cell data types are d.p.
*/
CELLTYPECHK2 ( CHK_STANDARD, "gfpa_c", SPICE_DP, cnfine, result );
/*
Initialize the input cells if necessary.
*/
CELLINIT2 ( cnfine, result );
/*
Check the input strings to make sure each pointer is non-null
and each string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "gfpa_c", target );
CHKFSTR ( CHK_STANDARD, "gfpa_c", illmn );
CHKFSTR ( CHK_STANDARD, "gfpa_c", abcorr );
CHKFSTR ( CHK_STANDARD, "gfpa_c", obsrvr );
CHKFSTR ( CHK_STANDARD, "gfpa_c", relate );
/*
Check the workspace size; some mallocs have a violent
dislike for negative allocation amounts. To be safe,
rule out a count of zero intervals as well.
*/
if ( nintvls < 1 )
{
setmsg_c ( "The specified workspace interval count # was "
"less than the minimum allowed value (1)." );
errint_c ( "#", nintvls );
sigerr_c ( "SPICE(VALUEOUTOFRANGE)" );
chkout_c ( "gfpa_c" );
return;
}
/*
Allocate the workspace.
We have `nw' "doublereal" cells, each having cell size 2*nintvls.
Each cell also has a control area containing SPICE_CELL_CTRLSZ
double precision values.
*/
nintvls = nintvls * 2;
nBytes = ( nintvls + SPICE_CELL_CTRLSZ ) * nw * sizeof(SpiceDouble);
work = (doublereal *) alloc_SpiceMemory( nBytes );
if ( !work )
{
setmsg_c ( "Workspace allocation of # bytes failed due to "
"malloc failure" );
errint_c ( "#", nBytes );
sigerr_c ( "SPICE(MALLOCFAILURE)" );
chkout_c ( "gfpa_c" );
return;
}
/*
Let the f2'd routine do the work.
*/
gfpa_ ( ( char * ) target,
( char * ) illmn,
( char * ) abcorr,
( char * ) obsrvr,
( char * ) relate,
( doublereal * ) &refval,
( doublereal * ) &adjust,
( doublereal * ) &step,
( doublereal * ) (cnfine->base),
( integer * ) &nintvls,
( integer * ) &nw,
( doublereal * ) work,
( doublereal * ) (result->base),
( ftnlen ) strlen(target),
( ftnlen ) strlen(illmn),
( ftnlen ) strlen(abcorr),
( ftnlen ) strlen(obsrvr),
( ftnlen ) strlen(relate) );
/*
De-allocate the workspace.
*/
free_SpiceMemory( work );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, result ) ;
}
ALLOC_CHECK;
chkout_c ( "gfpa_c" );
} /* End gfpa_c */
void repmi_c ( ConstSpiceChar * in,
ConstSpiceChar * marker,
SpiceInt value,
SpiceInt lenout,
SpiceChar * out )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
in I Input string.
marker I Marker to be replaced.
value I Replacement value.
lenout I Available space in output string.
out O Output string.
MAXLI P Maximum length of an integer.
-Detailed_Input
in is an arbitrary character string.
marker is an arbitrary character string. The first occurrence
of marker in the input string is to be replaced by value.
Leading and trailing blanks in marker are NOT significant.
In particular, no substitution is performed if marker
is blank.
value is an arbitrary integer.
lenout is the allowed length of the output string. This length
must large enough to hold the output string plus the
terminator. If the output string is expected to have x
characters, lenout should be at least x + 1.
-Detailed_Output
out is the string obtained by substituting the text
representation of value for the first occurrence
of marker in the input string.
out and in must be identical or disjoint.
-Parameters
MAXLI is the maximum expected length of the text
representation of an integer. 11 characters are
sufficient to hold any integer whose absolute
value is less than 10 billion.
This routine assumes that the input integer
is such that its string representation contains
no more than MAXLI characters.
-Files
None.
-Exceptions
1) The error SPICE(NULLPOINTER) is signaled if any of
the input or output string pointers is null.
2) If the marker string is blank or empty, this routine leaves
the input string unchanged, except that trailing blanks
will be trimmed. This case is not considered an error.
3) If the output string is too short to accommodate a terminating
null character, the error SPICE(STRINGTOOSHORT) is signaled.
4) If out does not have sufficient length to accommodate the
result of the substitution, the result will be truncated on
the right.
-Particulars
This is one of a family of related routines for inserting values
into strings. They are typically to construct messages that
are partly fixed, and partly determined at run time. For example,
a message like
"Fifty-one pictures were found in directory [USER.DATA]."
might be constructed from the fixed string
"#1 pictures were found in directory #2."
by the calls
#include "SpiceUsr.h"
.
.
.
#define LENOUT 81
.
.
.
repmct_c ( string, "#1", 51, 'c', LENOUT, string );
repmc_c ( string, "#2", "[USER.DATA]", LENOUT, string );
which substitute the cardinal text "Fifty-one" and the character
string "[USER.DATA]" for the markers "#1" and "#2" respectively.
The complete list of routines is shown below.
repmc_c ( Replace marker with character string value )
repmd_c ( Replace marker with double precision value )
repmf_c ( Replace marker with formatted d.p. value )
repmi_c ( Replace marker with integer value )
repmct_c ( Replace marker with cardinal text )
repmot_c ( Replace marker with ordinal text )
-Examples
1. Let
in == "Invalid operation value. The value was <opcode>."
Then following the call,
#include "SpiceUsr.h"
.
.
.
#define LENOUT 201
.
.
.
repmi_c ( in, "<opcode>", 5, LENOUT, outstr );
outstr contains the string:
"Invalid operation value. The value was 5."
2. Let
in == "Left endpoint exceeded right endpoint. "
"The left endpoint was: XX. The right "
"endpoint was: XX."
Then following the call,
#include "SpiceUsr.h"
.
.
.
#define LENOUT 201
.
.
.
repmi_c ( in, " XX ", 5, LENOUT, out );
out is
"Left endpoint exceeded right endpoint. The left "
"endpoint was: 5. The right endpoint was: XX."
3. Let
num == 23
chance == "fair"
score == 4.665
Then following the sequence of calls,
#include "SpiceUsr.h"
.
.
.
#define LENOUT 201
.
.
.
repmi_c ( "There are & routines that have a "
"& chance of meeting your needs."
"The maximum score was &.",
"&",
num,
LENOUT,
msg );
repmc_c ( msg, marker, chance, LENOUT, msg );
repmf_c ( msg, marker, score, 4, 'f', LENOUT, msg );
msg is
"There are 23 routines that have a fair chance of "
"meeting your needs. The maximum score was 4.665."
-Restrictions
None.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
I.M. Underwood (JPL)
-Version
-CSPICE Version 1.0.0, 14-AUG-2002 (NJB) (IMU)
-Index_Entries
replace marker with integer
-&
*/
{ /* Begin repmi_c */
/*
Local variables
*/
ConstSpiceChar * markPtr;
/*
Use discovery check-in.
Make sure no string argument pointers are null.
*/
CHKPTR( CHK_DISCOVER, "repmi_c", in );
CHKPTR( CHK_DISCOVER, "repmi_c", marker );
CHKPTR( CHK_DISCOVER, "repmi_c", out );
/*
If the output string can't hold a terminating null character,
we can't proceed.
*/
if ( lenout < 1 )
{
chkin_c ( "repmi_c" );
setmsg_c ( "String length lenout must be >= 1; actual "
"value = #." );
errint_c ( "#", lenout );
sigerr_c ( "SPICE(STRINGTOOSHORT)" );
chkout_c ( "repmi_c" );
return;
}
/*
If the output string has no room for data characters, we simply
terminate the string.
*/
if ( lenout == 1 )
{
out[0] = NULLCHAR;
return;
}
/*
If the input string has zero length, the output is empty as well.
*/
if ( in[0] == NULLCHAR )
{
out[0] = NULLCHAR;
return;
}
/*
If the marker is empty, pass a blank marker to the f2c'd routine.
Otherwise, pass in the marker.
*/
if ( marker[0] == NULLCHAR )
{
markPtr = " ";
}
else
{
markPtr = marker;
}
/*
Simply call the f2c'd routine.
*/
repmi_ ( ( char * ) in,
( char * ) markPtr,
( integer * ) &value,
( char * ) out,
( ftnlen ) strlen(in),
( ftnlen ) strlen(markPtr),
( ftnlen ) lenout-1 );
/*
Convert the output string from Fortran to C style.
*/
F2C_ConvertStr ( lenout, out );
} /* End repmi_c */
void insrti_c ( SpiceInt item,
SpiceCell * set )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
item I Item to be inserted.
set I/O Insertion set.
-Detailed_Input
item is an item which is to be inserted into the
specified set. item may or may not already
be an element of the set.
set is a CSPICE set. set must be declared as an integer
SpiceCell.
On input, set may or may not contain the input item
as an element.
-Detailed_Output
set on output contains the union of the input set and
the singleton set containing the input item.
-Parameters
None.
-Exceptions
1) If the input set argument is a SpiceCell of type other than
integer, the error SPICE(TYPEMISMATCH) is signaled.
2) If the insertion of the element into the set causes an excess
of elements, the error SPICE(SETEXCESS) is signaled.
3) If the input set argument does not qualify as a CSPICE set,
the error SPICE(NOTASET) will be signaled. CSPICE sets have
their data elements sorted in increasing order and contain
no duplicate data elements.
-Files
None.
-Particulars
None.
-Examples
1) In the following example, the NAIF ID code of Pluto is removed from
the integer set planets and inserted into the integer set
asteroids.
#include "SpiceUsr.h"
.
.
.
/.
Declare the sets with maximum number of elements MAXSIZ.
./
SPICEINT_CELL ( planets, MAXSIZ );
SPICEINT_CELL ( asteroids, MAXSIZ );
.
.
.
removi_c ( 999, &planets );
insrti_c ( 999, &asteroids );
If 999 is not an element of planets, then the contents of
planets are not changed. Similarly, if 999 is already an
element of asteroids, the contents of asteroids remain unchanged.
-Restrictions
None.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
C.A. Curzon (JPL)
W.L. Taber (JPL)
I.M. Underwood (JPL)
-Version
-CSPICE Version 2.0.0, 01-NOV-2005 (NJB)
Long error message was updated to include size of
set into which insertion was attempted.
-CSPICE Version 1.0.0, 07-AUG-2002 (NJB) (CAC) (WLT) (IMU)
-Index_Entries
insert an item into an integer set
-&
*/
{
/*
local variables
*/
SpiceBoolean inSet;
SpiceInt i;
SpiceInt * idata;
SpiceInt loc;
/*
Use discovery check-in.
*/
/*
Make sure we're working with an integer cell.
*/
CELLTYPECHK ( CHK_DISCOVER, "insrti_c", SPICE_INT, set );
idata = (SpiceInt *) (set->data);
/*
Make sure the cell is really a set.
*/
CELLISSETCHK ( CHK_DISCOVER, "insrti_c", set );
/*
Initialize the set if necessary.
*/
CELLINIT ( set );
/*
Is the item already in the set? If not, it needs to be inserted.
*/
loc = lstlei_c ( item, set->card, idata );
inSet = ( loc > -1 ) && ( item == idata[loc] );
if ( inSet )
{
return;
}
/*
It's an error if the set has no room left.
*/
if ( set->card == set->size )
{
chkin_c ( "insrti_c" );
setmsg_c ( "An element could not be inserted into the set "
"due to lack of space; set size is #." );
errint_c ( "#", set->size );
sigerr_c ( "SPICE(SETEXCESS)" );
chkout_c ( "insrti_c" );
return;
}
/*
Make room by moving the items that come after item in the set.
Insert the item after index loc.
*/
for ( i = (set->card); i > loc+1; i-- )
{
idata[i] = idata[i-1];
}
idata[loc+1] = item;
/*
Increment the set's cardinality.
*/
(set->card) ++;
/*
Sync the set.
*/
zzsynccl_c ( C2F, set );
}
void ekaclc_c ( SpiceInt handle,
SpiceInt segno,
ConstSpiceChar * column,
SpiceInt vallen,
const void * cvals,
ConstSpiceInt * entszs,
ConstSpiceBoolean * nlflgs,
ConstSpiceInt * rcptrs,
SpiceInt * wkindx )
/*
-Brief_I/O
Variable I/O Description
-------- --- --------------------------------------------------
handle I EK file handle.
segno I Number of segment to add column to.
column I Column name.
vallen I Length of character values.
cvals I Character values to add to column.
entszs I Array of sizes of column entries.
nlflgs I Array of null flags for column entries.
rcptrs I Record pointers for segment.
wkindx I-O Work space for column index.
-Detailed_Input
handle the handle of an EK file that is open for writing.
A "begin segment for fast write" operation must
have already been performed for the designated
segment.
segno is the number of the segment to which data is to be
added. Segments are numbered from 0 to nseg-1, where
nseg is the count of segments in the file.
column is the name of the column to be added. All of
the data for the named column will be added in
one shot.
vallen is the length of the strings in the cvals array.
The array should be declared with dimensions
[nrows][vallen]
where nrows is the number of rows in the column.
cvals is an array containing the entire set of column
entries for the specified column. The entries
are listed in row-order: the column entry for the
first row of the segment is first, followed by the
column entry for the second row, and so on. The
number of column entries must match the declared
number of rows in the segment. For columns having
fixed-size entries, a null entry must be allocated
the same amount of space occupied by a non-null
entry in the array cvals. For columns having
variable-size entries, null entries do not require
any space in the cvals* array, but in any case must
have their allocated space described correctly by
the corresponding element of the entszs array
(described below).
entszs is an array containing sizes of column entries.
The Ith element of entszs gives the size of the
Ith column entry. entszs is used only for columns
having variable-size entries. For such columns,
the dimension of entszs must be at least nrows.
The size of null entries should be set to zero.
For columns having fixed-size entries, the
dimension of this array may be any positive value.
nlflgs is an array of logical flags indicating whether
the corresponding entries are null. If the Ith
element of nlflgs is SPICEFALSE, the Ith column entry
defined by cvals and entszs is added to the
current segment in the specified kernel file.
If the Ith element of nlfgls is SPICETRUE, the
contents of the Ith column entry are undefined.
nlflgs is used only for columns that allow null
values; it's ignored for other columns.
rcptrs is an array of record pointers for the input
segment. This array is obtained as an output
from ekifld_c, the routine called to initiate a
fast write.
wkindx is a work space array used for building a column
index. If the column is indexed, the dimension of
wkindx_c must be at nrows, where nrows is the number
of rows in the column. If the column is not
indexed, this work space is not used, so the
dimension may be any positive value.
-Detailed_Output
None. See $Particulars for a description of the effect of this
routine.
-Parameters
None.
-Exceptions
1) If handle is invalid, the error will be diagnosed by routines
called by this routine.
2) If column is not the name of a declared column, the error
SPICE(NOCOLUMN) will be signaled.
3) If column specifies a column of whose data type is not
character, the error SPICE(WRONGDATATYPE) will be
signalled.
4) If the specified column already contains ANY entries, the
error will be diagnosed by routines called by this routine.
5) If an I/O error occurs while reading or writing the indicated
file, the error will be diagnosed by routines called by this
routine.
6) If the string pointer for column is null, the error
SPICE(NULLPOINTER) will be signaled.
7) If the input string column has length zero, the error
SPICE(EMPTYSTRING) will be signaled.
8) If the string pointer for cvals is null, the error
SPICE(NULLPOINTER) will be signaled.
9) If the string length vallen is less than 2, the error
SPICE(STRINGTOOSHORT) will be signaled.
-Files
See the EK Required Reading for a discussion of the EK file
format.
-Particulars
This routine operates by side effects: it modifies the named
EK file by adding data to the specified column. This routine
writes the entire contents of the specified column in one shot.
This routine creates columns much more efficiently than can be
done by sequential calls to ekacec_c, but has the drawback that
the caller must use more memory for the routine's inputs. This
routine cannot be used to add data to a partially completed
column.
-Examples
1) Suppose we have an E-kernel named order_db.ek which contains
records of orders for data products. The E-kernel has a
table called DATAORDERS that consists of the set of columns
listed below:
DATAORDERS
Column Name Data Type
----------- ---------
ORDER_ID INTEGER
CUSTOMER_ID INTEGER
LAST_NAME CHARACTER*(*)
FIRST_NAME CHARACTER*(*)
ORDER_DATE TIME
COST DOUBLE PRECISION
The order database also has a table of items that have been
ordered. The columns of this table are shown below:
DATAITEMS
Column Name Data Type
----------- ---------
ITEM_ID INTEGER
ORDER_ID INTEGER
ITEM_NAME CHARACTER*(*)
DESCRIPTION CHARACTER*(*)
PRICE DOUBLE PRECISION
We'll suppose that the file ORDER_DB.EK contains two segments,
the first containing the DATAORDERS table and the second
containing the DATAITEMS table.
Below, we show how we'd open a new EK file and create the
first of the segments described above.
#include "SpiceUsr.h"
#include <stdio.h>
void main()
{
/.
Constants
./
#define CNMLEN ( CSPICE_EK_COL_NAM_LEN + 1 )
#define DECLEN 201
#define EKNAME "order_db.ek"
#define FNMLEN 50
#define IFNAME "Test EK/Created 20-SEP-1995"
#define LNMLEN 50
#define LSK "leapseconds.ker"
#define NCOLS 6
#define NRESVC 0
#define NROWS 9
#define TABLE "DATAORDERS"
#define TNMLEN CSPICE_EK_TAB_NAM_LEN
#define UTCLEN 30
/.
Local variables
./
SpiceBoolean nlflgs [ NROWS ];
SpiceChar cdecls [ NCOLS ] [ DECLEN ];
SpiceChar cnames [ NCOLS ] [ CNMLEN ];
SpiceChar fnames [ NROWS ] [ FNMLEN ];
SpiceChar lnames [ NROWS ] [ LNMLEN ];
SpiceChar dateStr [ UTCLEN ];
SpiceDouble costs [ NROWS ];
SpiceDouble ets [ NROWS ];
SpiceInt cstids [ NROWS ];
SpiceInt ordids [ NROWS ];
SpiceInt handle;
SpiceInt i;
SpiceInt rcptrs [ NROWS ];
SpiceInt segno;
SpiceInt sizes [ NROWS ];
SpiceInt wkindx [ NROWS ];
/.
Load a leapseconds kernel for UTC/ET conversion.
./
furnsh_c ( LSK );
/.
Open a new EK file. For simplicity, we will not
reserve any space for the comment area, so the
number of reserved comment characters is zero.
The constant IFNAME is the internal file name.
./
ekopn_c ( EKNAME, IFNAME, NRESVC, &handle );
/.
Set up the table and column names and declarations
for the DATAORDERS segment. We'll index all of
the columns. All columns are scalar, so we omit
the size declaration. Only the COST column may take
null values.
./
strcpy ( cnames[0], "ORDER_ID" );
strcpy ( cdecls[0], "DATATYPE = INTEGER, INDEXED = TRUE" );
strcpy ( cnames[1], "CUSTOMER_ID" );
strcpy ( cdecls[1], "DATATYPE = INTEGER, INDEXED = TRUE" );
strcpy ( cnames[2], "LAST_NAME" );
strcpy ( cdecls[2], "DATATYPE = CHARACTER*(*),"
"INDEXED = TRUE" );
strcpy ( cnames[3], "FIRST_NAME" );
strcpy ( cdecls[3], "DATATYPE = CHARACTER*(*),"
"INDEXED = TRUE" );
strcpy ( cnames[4], "ORDER_DATE" );
strcpy ( cdecls[4], "DATATYPE = TIME, INDEXED = TRUE" );
strcpy ( cnames[5], "COST" );
strcpy ( cdecls[5], "DATATYPE = DOUBLE PRECISION,"
"INDEXED = TRUE,"
"NULLS_OK = TRUE" );
/.
Start the segment. We presume the number of rows
of data is known in advance.
./
ekifld_c ( handle, TABLE, NCOLS, NROWS, CNMLEN,
cnames, DECLEN, cdecls, &segno, rcptrs );
/.
At this point, arrays containing data for the
segment's columns may be filled in. The names
of the data arrays are shown below.
Column Data array
"ORDER_ID" ordids
"CUSTOMER_ID" cstids
"LAST_NAME" lnames
"FIRST_NAME" fnames
"ORDER_DATE" odates
"COST" costs
The null flags array indicates which entries are null.
It is ignored for columns that don't allow null
values. In this case, only the COST column allows
nulls.
Fill in data arrays and null flag arrays here. This code
section would normally be replaced by calls to user functions
returning column values.
./
for ( i = 0; i < NROWS; i++ )
{
ordids[i] = i;
cstids[i] = i*100;
costs [i] = (SpiceDouble) 100*i;
sprintf ( fnames[i], "Order %d Customer first name", i );
sprintf ( lnames[i], "Order %d Customer last name", i );
sprintf ( dateStr, "1998 Mar %d", i );
utc2et_c ( dateStr, ets+i );
nlflgs[i] = SPICEFALSE;
}
nlflgs[1] = SPICETRUE;
/.
The sizes array shown below is ignored for scalar
and fixed-size array columns, so we need not
initialize it. For variable-size arrays, the
Ith element of the sizes array must contain the size
of the Ith column entry in the column being written.
Normally, the sizes array would be reset for each
variable-size column.
Add the columns of data to the segment. All of the
data for each column is written in one shot.
./
ekacli_c ( handle, segno, "order_id", ordids,
sizes, nlflgs, rcptrs, wkindx );
ekacli_c ( handle, segno, "customer_id", cstids,
sizes, nlflgs, rcptrs, wkindx );
ekaclc_c ( handle, segno, "last_name", LNMLEN,
lnames, sizes, nlflgs, rcptrs, wkindx );
ekaclc_c ( handle, segno, "first_name", FNMLEN,
fnames, sizes, nlflgs, rcptrs, wkindx );
ekacld_c ( handle, segno, "order_date", ets,
sizes, nlflgs, rcptrs, wkindx );
ekacld_c ( handle, segno, "cost", costs,
sizes, nlflgs, rcptrs, wkindx );
/.
Complete the segment. The rcptrs array is that
returned by ekifld_c.
./
ekffld_c ( handle, segno, rcptrs );
/.
At this point, the second segment could be
created by an analogous process. In fact, the
second segment could be created at any time; it is
not necessary to populate the first segment with
data before starting the second segment.
The file must be closed by a call to ekcls_c.
./
ekcls_c ( handle );
}
-Restrictions
1) Only one segment can be created at a time using the fast
write routines.
2) No other EK operation may interrupt a fast write. For
example, it is not valid to issue a query while a fast write
is in progress.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
-Version
-CSPICE Version 1.2.2, 14-AUG-2006 (EDW)
Replace mention of ldpool_c with furnsh_c.
-CSPICE Version 1.2.1, 09-JAN-2002 (NJB)
Documentation change: instances of the phrase "fast load"
were replaced with "fast write."
Const-qualified input array cvals.
-CSPICE Version 1.1.0, 12-JUL-1998 (NJB)
Bug fix: now counts elements rather than rows for vector-valued
columns.
Bug fix: now uses dynamically allocated array of type logical
to interface with underlying f2c'd function ekaclc_.
Now maps segno from C to Fortran range.
Added "undef" of masking macro. Changed input pointer types
to pointers to const objects.
Replaced eksdsc_ call with ekssum_c call. This removes unsightly
references to segment descriptor alignments.
Fixed some chkout_c calls which referenced ekifld_c.
-CSPICE Version 1.0.0, 25-FEB-1999 (NJB)
Based on SPICELIB Version 1.0.0, 08-NOV-1995 (NJB)
-Index_Entries
write entire character column to EK segment
-&
*/
{ /* Begin ekaclc_c */
/*
Local variables
*/
SpiceBoolean fnd;
logical * logicalFlags;
SpiceEKSegSum summary;
SpiceChar ** cvalsPtr;
SpiceChar * fCvalsArr;
SpiceInt i;
SpiceInt fCvalsLen;
SpiceInt fSegno;
SpiceInt ncols;
SpiceInt nelts;
SpiceInt nrows;
SpiceInt size;
/*
Participate in error tracing.
*/
chkin_c ( "ekaclc_c" );
/*
Check the column name to make sure the pointer is non-null
and the string length is non-zero.
*/
CHKFSTR ( CHK_STANDARD, "ekaclc_c", column );
/*
Check the value array to make sure the pointer is non-null
and the string length is non-zero. Note: this check is normally
done for output strings: CHKOSTR is the macro that does the job.
*/
CHKOSTR ( CHK_STANDARD, "ekaclc_c", cvals, vallen );
/*
Get the row count for this segment.
*/
ekssum_c ( handle, segno, &summary );
nrows = summary.nrows;
/*
Locate the index of this column in the segment descriptor.
*/
ncols = summary.ncols;
i = 0;
fnd = SPICEFALSE;
while ( ( i < ncols ) && ( !fnd ) )
{
if ( eqstr_c( column, summary.cnames[i] ) )
{
fnd = SPICETRUE;
}
else
{
i++;
}
}
if ( !fnd )
{
setmsg_c ( "Column <#> does not belong to segment #. " );
errch_c ( "#", column );
errint_c ( "#", segno );
sigerr_c ( "SPICE(NOCOLUMN)" );
chkout_c ( "ekaclc_c" );
return;
}
/*
Now i is the index within the segment descriptor of the column
descriptor for the column of interest. Get the dimension information
for this column.
*/
size = summary.cdescrs[i].size;
/*
Compute the total string count of the input array. If the column
has fixed-size entries, we ignore the entszs array. Otherwise, the
entszs array tells us how many strings we're getting.
*/
if ( size == SPICE_EK_VARSIZ )
{
nelts = sumai_c ( entszs, nrows );
}
else
{
nelts = nrows * size;
}
/*
Allocate an array of logicals and assign values from the input
array of SpiceBooleans.
*/
logicalFlags = ( logical * ) malloc ( nelts * sizeof(logical) );
if ( !logicalFlags )
{
setmsg_c ( "Failure on malloc call to create null flag array "
"for column values." );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "ekaclc_c" );
return;
}
/*
Copy the input null flags to our array of type logical.
*/
for ( i = 0; i < nrows; i++ )
{
logicalFlags[i] = nlflgs[i];
}
/*
We need to make a blank-padded version of the cvals array.
We'll first allocate an array of character pointers to index
the values, initialize this array, and use it to produce
a dynamically allocated array of Fortran-style strings.
*/
cvalsPtr = ( SpiceChar ** ) malloc ( nelts * sizeof(SpiceChar *) );
if ( cvalsPtr == 0 )
{
free ( logicalFlags );
setmsg_c ( "Failure on malloc call to create pointer array "
"for column values." );
sigerr_c ( "SPICE(MALLOCFAILED)" );
chkout_c ( "ekaclc_c" );
return;
}
for ( i = 0; i < nelts; i++ )
{
cvalsPtr[i] = (SpiceChar *)cvals + ( i * vallen );
}
C2F_CreateFixStrArr ( nelts,
vallen,
( ConstSpiceChar ** ) cvalsPtr,
&fCvalsLen,
&fCvalsArr );
if ( failed_c() )
{
free ( logicalFlags );
free ( cvalsPtr );
chkout_c ( "ekaclc_c" );
return;
}
/*
Map the segment number to the Fortran range.
*/
fSegno = segno + 1;
ekaclc_ ( ( integer * ) &handle,
( integer * ) &fSegno,
( char * ) column,
( char * ) fCvalsArr,
( integer * ) entszs,
( logical * ) logicalFlags,
( integer * ) rcptrs,
( integer * ) wkindx,
( ftnlen ) strlen(column),
( ftnlen ) fCvalsLen );
/*
Clean up all of our dynamically allocated arrays.
*/
free ( cvalsPtr );
free ( fCvalsArr );
free ( logicalFlags );
chkout_c ( "ekaclc_c" );
} /* End ekaclc_c */
void union_c ( SpiceCell * a,
SpiceCell * b,
SpiceCell * c )
/*
-Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
a I First input set.
b I Second input set.
c O Union of a and b.
-Detailed_Input
a is a CSPICE set. a must be declared as a SpiceCell
of data type character, double precision, or integer.
b is a CSPICE set, distinct from a. b must have the
same data type as a.
-Detailed_Output
c is a CSPICE set, distinct from sets a and b, which
contains the union of a and b (that is, all of
the elements which are in a or b or both). c must
have the same data type as a and b.
When comparing elements of character sets, this routine
ignores trailing blanks. Trailing blanks will be
trimmed from the members of the output set c.
-Parameters
None.
-Exceptions
1) If the input set arguments don't have identical data types,
the error SPICE(TYPEMISMATCH) is signaled.
2) If the union of the two sets contains more elements than can be
contained in the output set, the error SPICE(SETEXCESS) is signaled.
3) If the set arguments have character type and the length of the
elements of the output set is less than the maximum of the
lengths of the elements of the input sets, the error
SPICE(ELEMENTSTOOSHORT) is signaled.
4) If either of the input arguments may be unordered or contain
duplicates, the error SPICE(NOTASET) is signaled.
-Files
None.
-Particulars
This is a generic CSPICE set routine; it operates on sets of any
supported data type.
The union of two sets contains every element which is
in the first set, or in the second set, or in both sets.
{a,b} union {c,d} = {a,b,c,d}
{a,b,c} {b,c,d} {a,b,c,d}
{a,b,c,d} {} {a,b,c,d}
{} {a,b,c,d} {a,b,c,d}
{} {} {}
-Examples
1) The following code fragment places the union of the character sets
planets and asteroids into the character set result.
#include "SpiceUsr.h"
.
.
.
/.
Declare the sets with string length NAMLEN and with maximum
number of elements MAXSIZ.
./
SPICECHAR_CELL ( planets, MAXSIZ, NAMLEN );
SPICECHAR_CELL ( asteroids, MAXSIZ, NAMLEN );
SPICECHAR_CELL ( result, MAXSIZ, NAMLEN );
.
.
.
/.
Compute the union.
./
union_c ( &planets, &asteroids, &result );
2) Repeat example #1, this time using integer sets containing
ID codes of the bodies of interest.
#include "SpiceUsr.h"
.
.
.
/.
Declare the sets with maximum number of elements MAXSIZ.
./
SPICEINT_CELL ( planets, MAXSIZ );
SPICEINT_CELL ( asteroids, MAXSIZ );
SPICEINT_CELL ( result, MAXSIZ );
.
.
.
/.
Compute the union.
./
union_c ( &planets, &asteroids, &result );
3) Construct a set containing the periapse and apoapse TDB epochs
of an orbiter, given two separate sets containing the epochs of
those events.
#include "SpiceUsr.h"
.
.
.
/.
Declare the sets with maximum number of elements MAXSIZ.
./
SPICEDOUBLE_CELL ( periapse, MAXSIZ );
SPICEDOUBLE_CELL ( apoapse, MAXSIZ );
SPICEDOUBLE_CELL ( result, MAXSIZ );
.
.
.
/.
Compute the union.
./
union_c ( &periapse, &apoapse, &result );
-Restrictions
1) The output set must be distinct from both of the input sets.
For example, the following calls are invalid.
union_c ( ¤t, &new, ¤t );
union_c ( &new, ¤t, ¤t );
In each of the examples above, whether or not the subroutine
signals an error, the results will almost certainly be wrong.
Nearly the same effect can be achieved, however, by placing the
result into a temporary set, which is immediately copied back
into one of the input sets, as shown below.
union_c ( ¤t, &new, &temp );
copy_c ( &temp, &new );
2) String comparisons performed by this routine are Fortran-style:
trailing blanks in the input sets are ignored. This gives
consistent behavior with CSPICE code generated by the f2c
translator, as well as with the Fortran SPICE Toolkit.
Note that this behavior is not identical to that of the ANSI
C library functions strcmp and strncmp.
-Literature_References
None.
-Author_and_Institution
N.J. Bachman (JPL)
C.A. Curzon (JPL)
W.L. Taber (JPL)
I.M. Underwood (JPL)
-Version
-CSPICE Version 1.1.0, 15-FEB-2005 (NJB)
Bug fix: loop bound changed from 2 to 3 in loop used
to free dynamically allocated arrays.
-CSPICE Version 1.0.0, 08-AUG-2002 (NJB) (CAC) (WLT) (IMU)
-Index_Entries
union of two sets
-&
*/
{ /* Begin union_c */
/*
Local variables
*/
SpiceChar * fCell[3];
SpiceInt fLen [3];
SpiceInt i;
/*
Standard SPICE error handling.
*/
if ( return_c() )
{
return;
}
chkin_c ( "union_c" );
/*
Make sure data types match.
*/
CELLMATCH3 ( CHK_STANDARD, "union_c", a, b, c );
/*
Make sure the input cells are sets.
*/
CELLISSETCHK2 ( CHK_STANDARD, "union_c", a, b );
/*
Initialize the cells if necessary.
*/
CELLINIT3 ( a, b, c );
/*
Call the union routine appropriate for the data type of the cells.
*/
if ( a->dtype == SPICE_CHR )
{
/*
Construct Fortran-style sets suitable for passing to unionc_.
*/
C2F_MAP_CELL3 ( "",
a, fCell, fLen,
b, fCell+1, fLen+1,
c, fCell+2, fLen+2 );
if ( failed_c() )
{
chkout_c ( "union_c" );
return;
}
unionc_ ( (char * ) fCell[0],
(char * ) fCell[1],
(char * ) fCell[2],
(ftnlen ) fLen[0],
(ftnlen ) fLen[1],
(ftnlen ) fLen[2] );
/*
Map the union back to a C style cell.
*/
F2C_MAP_CELL ( fCell[2], fLen[2], c );
/*
We're done with the dynamically allocated Fortran-style arrays.
*/
for ( i = 0; i < 3; i++ )
{
free ( fCell[i] );
}
}
else if ( a->dtype == SPICE_DP )
{
uniond_ ( (doublereal * ) (a->base),
(doublereal * ) (b->base),
(doublereal * ) (c->base) );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, c );
}
}
else if ( a->dtype == SPICE_INT )
{
unioni_ ( (integer * ) (a->base),
(integer * ) (b->base),
(integer * ) (c->base) );
/*
Sync the output cell.
*/
if ( !failed_c() )
{
zzsynccl_c ( F2C, c );
}
}
else
{
setmsg_c ( "Cell a contains unrecognized data type code #." );
errint_c ( "#", (SpiceInt) (a->dtype) );
sigerr_c ( "SPICE(NOTSUPPORTED)" );
chkout_c ( "union_c" );
return;
}
/*
Indicate the result is a set.
*/
c->isSet = SPICETRUE;
chkout_c ( "union_c" );
} /* End union_c */
