inline DsMagvar::DsMagvar(const char* file)
{
if (file != 0) {
geomag(12,file);
haveData = true;
}
else {
haveData = 0;
}
}
/* That's the worst code I've ever had to modify !!
* To test the function use lat=-40deg long=120deg altitude=0 date=2007.5 then myDeclinaison=14.75
* Declination is considered positive when the angle measured is east of true north and negative when west
* that means that heading_true_north = heading_magnetic_north - declination */
void DMU_comp_geomag(double decim_date, GPS_Struct gps, double *myDeclination)
{
static int maxdeg;
static float altm, dlat, dlon;
static float ati, adec, adip;
static float alt, time, dec, dip, ti, gv;
static float time1, dec1, dip1, ti1;
static float time2, dec2, dip2, ti2;
int warn_H, warn_H_strong, warn_P;
char fname[100] = "/WMM.COF";
char decd[5], dipd[5],d_str[81],modl[20];
float x1,x2,y1,y2,z1,z2,h1,h2;
float ax,ay,az,ah;
float rTd=0.017453292;
float epochlowlim,epochuplim;
float epochrange = 5.0;
float warn_H_val, warn_H_strong_val;
FILE *wmmtemp;
printf("Before fopen\n");
wmmtemp = fopen(fname,"r");
if(wmmtemp == NULL)
{
printf("DMU_comp_geomag -> Could not open %s\n", fname);
printf("Download it from http://www.ngdc.noaa.gov/seg/WMM/\n");
*myDeclination = 0.0;
return;
}
printf("Now we read the file\n");
fgets(d_str, 80, wmmtemp);
sscanf(d_str,"%f%s",&epochlowlim,modl);
fclose(wmmtemp);
printf("Read of %s success\n", fname);
/* strcpy (goodbye,"\n -- End of WMM Point Calculation Program -- \n\n");*/
/* INITIALIZE GEOMAG ROUTINE */
maxdeg = 12;
warn_H = 0;
warn_H_val = 99999.0;
warn_H_strong = 0;
warn_H_strong_val = 99999.0;
warn_P = 0;
geomag(&maxdeg);
dlat = -RAD2DEG(gps.latitude);
dlon = -RAD2DEG(gps.longitude);
altm = gps.altitude;
alt = altm/1000;
epochuplim = epochlowlim + epochrange;
if(decim_date < epochlowlim || decim_date > epochuplim)
{
fprintf(stderr, "Date bad range (%f)\n", decim_date);
fprintf(stderr, "ENTER TIME IN DECIMAL YEAR (%-7.2f - %-7.2f)\n",epochlowlim,epochuplim);
exit(EXIT_FAILURE);
}
time = decim_date;
geomg1(alt,dlat,dlon,time,&dec,&dip,&ti,&gv);
time1 = time;
dec1 = dec;
dip1 = dip;
ti1 = ti;
time = time1 + 1.0;
geomg1(alt,dlat,dlon,time,&dec,&dip,&ti,&gv);
time2 = time;
dec2 = dec;
dip2 = dip;
ti2 = ti;
/*COMPUTE X, Y, Z, AND H COMPONENTS OF THE MAGNETIC FIELD*/
x1=ti1*(cos((dec1*rTd))*cos((dip1*rTd)));
x2=ti2*(cos((dec2*rTd))*cos((dip2*rTd)));
y1=ti1*(cos((dip1*rTd))*sin((dec1*rTd)));
y2=ti2*(cos((dip2*rTd))*sin((dec2*rTd)));
z1=ti1*(sin((dip1*rTd)));
z2=ti2*(sin((dip2*rTd)));
h1=ti1*(cos((dip1*rTd)));
h2=ti2*(cos((dip2*rTd)));
/* COMPUTE ANNUAL CHANGE FOR TOTAL INTENSITY */
ati = ti2 - ti1;
/* COMPUTE ANNUAL CHANGE FOR DIP & DEC */
adip = (dip2 - dip1) * 60.;
adec = (dec2 - dec1) * 60.;
/* COMPUTE ANNUAL CHANGE FOR X, Y, Z, AND H */
ax = x2-x1;
ay = y2-y1;
az = z2-z1;
ah = h2-h1;
if (dec1 < 0.0) {
strcpy (decd,"(WEST)");
}
else
{
strcpy(decd,"(EAST)");
}
if (dip1 < 0.0)
{
strcpy(dipd,"(UP) ");
}
else
{
strcpy(dipd,"(DOWN)");
}
/* deal with geographic and magnetic poles */
if (h1 < 100.0) /* at magnetic poles */
{
dec1 = NaN;
adec = NaN;
strcpy(decd,"(VOID)");
/* while rest is ok */
}
if (h1 < 1000.0)
{
warn_H = 0;
warn_H_strong = 1;
warn_H_strong_val = h1;
}
else if (h1 < 5000.0 && !warn_H_strong)
{
warn_H = 1;
warn_H_val = h1;
}
if (90.0-fabs(dlat) <= 0.001) /* at geographic poles */
{
x1 = NaN;
y1 = NaN;
dec1 = NaN;
ax = NaN;
ay = NaN;
adec = NaN;
strcpy(decd,"(VOID)");
warn_P = 1;
warn_H = 0;
warn_H_strong = 0;
/* while rest is ok */
}
*myDeclination = DEG2RAD(dec1);
return;
}
