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#define PJ_LIB__
#include <math.h>
#include "proj.h"
#include "proj_internal.h"
PROJ_HEAD(eck2, "Eckert II") "\n\tPCyl, Sph";
#define FXC 0.46065886596178063902
#define FYC 1.44720250911653531871
#define C13 0.33333333333333333333
#define ONEEPS 1.0000001
static PJ_XY eck2_s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
PJ_XY xy = {0.0,0.0};
(void) P;
xy.x = FXC * lp.lam * (xy.y = sqrt(4. - 3. * sin(fabs(lp.phi))));
xy.y = FYC * (2. - xy.y);
if ( lp.phi < 0.) xy.y = -xy.y;
return (xy);
}
static PJ_LP eck2_s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
PJ_LP lp = {0.0,0.0};
(void) P;
lp.phi = 2. - fabs(xy.y) / FYC;
lp.lam = xy.x / (FXC * lp.phi);
lp.phi = (4. - lp.phi * lp.phi) * C13;
if (fabs(lp.phi) >= 1.) {
if (fabs(lp.phi) > ONEEPS) {
proj_errno_set(P, PROJ_ERR_COORD_TRANSFM_OUTSIDE_PROJECTION_DOMAIN);
return lp;
} else {
lp.phi = lp.phi < 0. ? -M_HALFPI : M_HALFPI;
}
} else
lp.phi = asin(lp.phi);
if (xy.y < 0)
lp.phi = -lp.phi;
return (lp);
}
PJ *PROJECTION(eck2) {
P->es = 0.;
P->inv = eck2_s_inverse;
P->fwd = eck2_s_forward;
return P;
}
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