void airsar_to_latlon(meta_parameters *meta,
double xSample, double yLine, double height,
double *lat, double *lon)
{
if (!meta->airsar)
asfPrintError("airsar_to_latlon() called with no airsar block!\n");
const double a = 6378137.0; // semi-major axis
const double b = 6356752.3412; // semi-minor axis
const double e2 = 0.00669437999014; // ellipticity
const double e12 = 0.00673949674228; // second eccentricity
// we try to cache the matrices needed for the computation
// this makes sure we don't reuse the cache incorrectly (i.e., on
// data (=> an airsar block) which doesn't match what we cached for)
static meta_airsar *cached_airsar_block = NULL;
// these are the cached transformation parameters
static matrix *m = NULL;
static double ra=-999, o1=-999, o2=-999, o3=-999;
if (!m)
m = matrix_alloc(3,3); // only needs to be done once
// if we aren't calculating with the exact same airsar block, we
// need to recalculate the transformation block
int recalc = !cached_airsar_block ||
cached_airsar_block->lat_peg_point != meta->airsar->lat_peg_point ||
cached_airsar_block->lon_peg_point != meta->airsar->lon_peg_point ||
cached_airsar_block->head_peg_point != meta->airsar->head_peg_point;
if (recalc) {
// cache airsar block, so we can be sure we're not reusing
// the stored data incorrectly
if (cached_airsar_block)
free(cached_airsar_block);
cached_airsar_block = meta_airsar_init();
*cached_airsar_block = *(meta->airsar);
asfPrintStatus("Calculating airsar transformation parameters...\n");
// now precalculate data
double lat_peg = meta->airsar->lat_peg_point*D2R;
double lon_peg = meta->airsar->lon_peg_point*D2R;
double head_peg = meta->airsar->head_peg_point*D2R;
double re = a / sqrt(1-e2*sin(lat_peg)*sin(lat_peg));
double rn = (a*(1-e2)) / pow(1-e2*sin(lat_peg)*sin(lat_peg), 1.5);
ra = (re*rn) / (re*cos(head_peg)*cos(head_peg)+rn*sin(head_peg)*sin(head_peg));
matrix *m1, *m2;
m1 = matrix_alloc(3,3);
m2 = matrix_alloc(3,3);
m1->coeff[0][0] = -sin(lon_peg);
m1->coeff[0][1] = -sin(lat_peg)*cos(lon_peg);
m1->coeff[0][2] = cos(lat_peg)*cos(lon_peg);
m1->coeff[1][0] = cos(lon_peg);
m1->coeff[1][1] = -sin(lat_peg)*sin(lon_peg);
m1->coeff[1][2] = cos(lat_peg)*sin(lon_peg);
m1->coeff[2][0] = 0.0;
m1->coeff[2][1] = cos(lat_peg);
m1->coeff[2][2] = sin(lat_peg);
m2->coeff[0][0] = 0.0;
m2->coeff[0][1] = sin(head_peg);
m2->coeff[0][2] = -cos(head_peg);
m2->coeff[1][0] = 0.0;
m2->coeff[1][1] = cos(head_peg);
m2->coeff[1][2] = sin(head_peg);
m2->coeff[2][0] = 1.0;
m2->coeff[2][1] = 0.0;
m2->coeff[2][2] = 0.0;
o1 = re*cos(lat_peg)*cos(lon_peg)-ra*cos(lat_peg)*cos(lon_peg);
o2 = re*cos(lat_peg)*sin(lon_peg)-ra*cos(lat_peg)*sin(lon_peg);
o3 = re*(1-e2)*sin(lat_peg)-ra*sin(lat_peg);
matrix_mult(m,m1,m2);
matrix_free(m1);
matrix_free(m2);
}
// Make sure we didn't miss anything
assert(ra != -999 && o1 != -999 && o2 != -999 && o3 != -999);
//------------------------------------------------------------------
// Now the actual computation, using the cached matrix etc
// convenience aliases
double c0 = meta->airsar->cross_track_offset;
double s0 = meta->airsar->along_track_offset;
double ypix = meta->general->y_pixel_size/meta->general->line_scaling;
double xpix = meta->general->x_pixel_size/meta->general->sample_scaling;
// radar coordinates
double c_lat = (xSample*xpix+c0)/ra;
double s_lon = (yLine*ypix+s0)/ra;
//height += meta->airsar->gps_altitude;
// radar coordinates in WGS84
double t1 = (ra+height)*cos(c_lat)*cos(s_lon);
double t2 = (ra+height)*cos(c_lat)*sin(s_lon);
double t3 = (ra+height)*sin(c_lat);
double c1 = m->coeff[0][0]*t1 + m->coeff[0][1]*t2 + m->coeff[0][2]*t3;
double c2 = m->coeff[1][0]*t1 + m->coeff[1][1]*t2 + m->coeff[1][2]*t3;
double c3 = m->coeff[2][0]*t1 + m->coeff[2][1]*t2 + m->coeff[2][2]*t3;
// shift into local Cartesian coordinates
double x = c1 + o1;// + 9.0;
double y = c2 + o2;// - 161.0;
double z = c3 + o3;// - 179.0;
// local Cartesian coordinates into geographic coordinates
double d = sqrt(x*x+y*y);
double theta = atan2(z*a, d*b);
*lat = R2D*atan2(z+e12*b*sin(theta)*sin(theta)*sin(theta),
d-e2*a*cos(theta)*cos(theta)*cos(theta));
*lon = R2D*atan2(y, x);
}
meta_parameters* airsar2meta(airsar_header *header,
airsar_param_header *params,
airsar_dem_header *dem)
{
meta_parameters *meta;
hms_time hms;
// Allocate memory for metadata structure
meta = raw_init();
// General block
sprintf(meta->general->basename, "%s", params->site_name);
sprintf(meta->general->sensor, "AIRSAR");
strcpy(meta->general->sensor_name, "SAR");
if (strlen(header->processor)>0) {
header->processor[4] = '\0';
strcpy(meta->general->processor, "JPL version ");
strcat(meta->general->processor, header->processor);
} else {
strcpy(meta->general->processor, MAGIC_UNSET_STRING);
}
// FIXME: various data types - InSAR vs. polarimetric
date_sec2hms(params->acquisition_seconds, &hms);
sprintf(meta->general->acquisition_date, "%s %d:%d:%.3lf",
params->acquisition_date, hms.hour, hms.min, hms.sec);
meta->general->orbit = params->cct_id; // close enough
// no frame number
// FIXME: decide how to separate interferometric/polarimetric data
meta->general->band_count = 1;
meta->general->line_count = header->line_count;
//header->line_count - header->first_data_offset / header->sample_count;
meta->general->sample_count = header->sample_count;
meta->general->start_line = 0;
meta->general->start_sample = 0;
meta->general->x_pixel_size = header->x_pixel_size;
meta->general->y_pixel_size = header->y_pixel_size;
meta->general->center_latitude = params->center_lat;
meta->general->center_longitude = params->center_lon;
meta->general->re_major = 6378137.0; // WGS84
meta->general->re_minor = 6356752.314; // WGS84
// no information on bit error rate, missing lines and no data
// SAR block
meta->sar = meta_sar_init();
// The CCT type 'CM' stands for 'Compressed Stokes Matrix' which implies
// that you have fully polarimetric data
if (strncmp_case(params->cct_type, "CM", 2) == 0) {
meta->general->image_data_type = POLARIMETRIC_IMAGE;
meta->general->radiometry = r_SIGMA;
strcpy(meta->sar->polarization, "QUAD-POL");
meta->general->band_count = 8;
}
if (strncmp_case(header->range_projection, "GROUND", 6) == 0)
meta->sar->image_type = 'G';
// no information on look direction
if (params->deskewed == 1)
meta->sar->deskewed = 1;
else if (params->deskewed == 2)
meta->sar->deskewed = 0;
meta->sar->original_line_count = header->line_count;
meta->sar->original_sample_count = header->sample_count;
meta->sar->line_increment = 1;
meta->sar->sample_increment = 1;
// no information on azimuth and range time per pixel
// no information on slant and time shift
meta->sar->slant_range_first_pixel = params->near_slant_range;
meta->sar->wavelength = params->wavelength;
meta->sar->prf = params->prf;
// no information on earth radius and satellite height
// no time information
// no Doppler information
meta->sar->azimuth_processing_bandwidth = params->chirp_bandwidth;
// no chirp rate information
meta->sar->pulse_duration = params->pulse_length;
meta->sar->range_sampling_rate = params->range_sampling_rate;
// FIXME: check polarizations for interferometric/polarimetric data
// FIXME: multilook flag depends on data type
// AirSAR block
meta->airsar = meta_airsar_init();
meta->airsar->scale_factor = 1.0; // Bruce Chapman said so.
meta->airsar->gps_altitude = params->gps_altitude;
if (dem) {
meta->airsar->lat_peg_point = dem->lat_peg_point;
meta->airsar->lon_peg_point = dem->lon_peg_point;
meta->airsar->head_peg_point = dem->head_peg_point;
meta->airsar->along_track_offset = dem->along_track_offset;
meta->airsar->cross_track_offset = dem->cross_track_offset;
}
else {
meta->airsar->lat_peg_point = params->lat_peg_point;
meta->airsar->lon_peg_point = params->lon_peg_point;
meta->airsar->head_peg_point = params->head_peg_point;
meta->airsar->along_track_offset = params->along_track_offset;
meta->airsar->cross_track_offset = params->cross_track_offset;
}
// The DEM header of Rick's prime test data did not have a valid peg point.
// Without that the other numbers (along-track and cross-track offsets
// as well as corner coordinates) don't make sense.
// Will take the numbers out of the parameter header. Seems to work fine
// with the prime test data set. Extract only elevation offset and increment
// out of the DEM header
if (dem) {
meta->airsar->elevation_increment = dem->elevation_increment;
meta->airsar->elevation_offset = dem->elevation_offset;
}
// Location block
meta->location = meta_location_init();
if (dem) {
meta->location->lat_start_near_range = dem->corner1_lat;
meta->location->lon_start_near_range = dem->corner1_lon;
meta->location->lat_start_far_range = dem->corner2_lat;
meta->location->lon_start_far_range = dem->corner2_lon;
meta->location->lat_end_near_range = dem->corner4_lat;
meta->location->lon_end_near_range = dem->corner4_lon;
meta->location->lat_end_far_range = dem->corner3_lat;
meta->location->lon_end_far_range = dem->corner3_lon;
}
return meta;
}
