source: Sophya/trunk/SophyaExt/XephemAstroLib/sphcart.c@ 1783

#include <math.h>
#include "P_.h"
#include "astro.h"

/* transformation from spherical to cartesian coordinates */
void
sphcart (l, b, r, x, y, z)
double l, b, r;         /* source: spherical coordinates */
double *x, *y, *z;      /* result: rectangular coordinates */
{
        double rcb = r * cos(b);

        *x = rcb * cos(l);
        *y = rcb * sin(l);
        *z = r * sin(b);
}

/* transformation from cartesian to spherical coordinates */
void
cartsph (x, y, z, l, b, r)
double x, y, z;         /* source: rectangular coordinates */
double *l, *b, *r;      /* result: spherical coordinates */
{
        double rho = x*x + y*y;

        if (rho > 1e-35) {      /* standard case: off axis */
            *l = atan2(y, x);
            range (l, 2*PI);
            *b = atan2(z, sqrt(rho));
            *r = sqrt(rho + z*z);
        } else {                /* degenerate case; avoid math error */
            *l = 0.0;
            if (z == 0.0)
                *b = 0.0;
            else
                *b = (z > 0.0) ? PI/2. : -PI/2.;
            *r = fabs(z);
        }
}

/* For RCS Only -- Do Not Edit */
static char *rcsid[2] = {(char *)rcsid, "@(#) $RCSfile: sphcart.c,v $ $Date: 2001-10-22 12:08:28 $ $Revision: 1.2 $ $Name: not supported by cvs2svn $"};