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#define PJ_LIB__
#include <math.h>
#include "proj.h"
#include "proj_internal.h"
PROJ_HEAD(collg, "Collignon") "\n\tPCyl, Sph";
#define FXC 1.12837916709551257390
#define FYC 1.77245385090551602729
#define ONEEPS 1.0000001
static PJ_XY collg_s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
PJ_XY xy = {0.0,0.0};
(void) P;
xy.y = 1. - sin(lp.phi);
if (xy.y <= 0.)
xy.y = 0.;
else
xy.y = sqrt(xy.y);
xy.x = FXC * lp.lam * xy.y;
xy.y = FYC * (1. - xy.y);
return (xy);
}
static PJ_LP collg_s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
PJ_LP lp = {0.0,0.0};
lp.phi = xy.y / FYC - 1.;
lp.phi = 1. - lp.phi * lp.phi;
if (fabs(lp.phi) < 1.)
lp.phi = asin(lp.phi);
else if (fabs(lp.phi) > ONEEPS) {
proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
return lp;
} else {
lp.phi = lp.phi < 0. ? -M_HALFPI : M_HALFPI;
}
lp.lam = 1. - sin(lp.phi);
if (lp.lam <= 0.)
lp.lam = 0.;
else
lp.lam = xy.x / (FXC * sqrt(lp.lam));
return (lp);
}
PJ *PROJECTION(collg) {
P->es = 0.0;
P->inv = collg_s_inverse;
P->fwd = collg_s_forward;
return P;
}
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