/Proj4/adjlon.c

 1/* reduce argument to range +/- PI */
 2#ifndef lint
 3static const char SCCSID[]="@(#)adjlon.c	4.3	93/06/12	GIE	REL";
 4#endif
 5#include <math.h>
 6#include "projects.h"
 7
 8#define SPI     3.14159265359
 9#define TWOPI   6.2831853071795864769
10#define ONEPI   3.14159265358979323846
11
12double adjlon (double lon) {
13    if (fabs(lon) <= SPI) return( lon );
14    lon += ONEPI;  /* adjust to 0..2pi rad */
15    lon -= TWOPI * floor(lon / TWOPI); /* remove integral # of 'revolutions'*/
16    lon -= ONEPI;  /* adjust back to -pi..pi rad */
17    return( lon );
18}