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/*****************************************************************************
* Johns Hopkins University
* Center For Astrophysical Sciences
* FUSE
*****************************************************************************
*
* Synopsis: int saa(saareg *saa, double lon, double lat)
*
* Description: Determines if FUSE is in the SAA for given models of the SAA
*
*
* Arguments: saareg *saa A structure containing data that roughly
* outlines the SAA region.
* (n_points: number of points
* lat: the latitude array
* lon: the longitude array)
* (currently we have only one model).
* double lon,lat Geocentric longitude and latitude of FUSE
*
* Returns: int 0 if not in SAA
* 1 if in SAA
*
* History: 07/17/98 E. Murphy Begin work.
* 06/22/99 peb Tidied code, added FITS_ wrappers,
* removed hardcoded variables.
* 07/02/99 peb Moved SAA data to a structure.
* 08/25/99 emm Fixed bug in setting maxlon
* 08/28/03 v1.3 bjg Adopt Bryce's algorithm for determining
* when FUSE is in the SAA.
* 08/28/03 v1.4 bjg v1.3 didn't compile but v1.4 does
* 08/29/03 v1.5 bjg slightly modified getDir
*
****************************************************************************/
#include "calfuse.h"
int getDir(double lon0,double lat0,double lon1,double lat1,double lon2,double lat2)
{
double dx1, dx2, dy1, dy2, t1, t2;
dx1=lon1-lon0; dy1=lat1-lat0;
dx2=lon2-lon0; dy2=lat2-lat0;
t1=dx1*dy2; t2=dy1*dx2;
if (t1>t2)
return(-1);
if (t1<t2)
return(1);
return(1);
}
int
saa(saareg *saa, double lon, double lat)
{
int i;
int dir=0;
int oldDir=0;
for (i=0; i<saa->n_points-1; i++) {
dir=getDir(lon,lat,(double)(saa->lon[i]),(double)(saa->lat[i]),(double)(saa->lon[i+1]),(double)(saa->lat[i+1]));
if (dir*oldDir<0)
return(0);
else
oldDir=dir;
}
return(1);
}
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