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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "projects.h"
namespace { // anonymous namespace
struct pj_opaque {
int vdg3;
};
} // anonymous namespace
PROJ_HEAD(vandg2, "van der Grinten II") "\n\tMisc Sph, no inv";
PROJ_HEAD(vandg3, "van der Grinten III") "\n\tMisc Sph, no inv";
#define TOL 1e-10
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double x1, at, bt, ct;
bt = fabs(M_TWO_D_PI * lp.phi);
if ((ct = 1. - bt * bt) < 0.)
ct = 0.;
else
ct = sqrt(ct);
if (fabs(lp.lam) < TOL) {
xy.x = 0.;
xy.y = M_PI * (lp.phi < 0. ? -bt : bt) / (1. + ct);
} else {
at = 0.5 * fabs(M_PI / lp.lam - lp.lam / M_PI);
if (Q->vdg3) {
x1 = bt / (1. + ct);
xy.x = M_PI * (sqrt(at * at + 1. - x1 * x1) - at);
xy.y = M_PI * x1;
} else {
x1 = (ct * sqrt(1. + at * at) - at * ct * ct) /
(1. + at * at * bt * bt);
xy.x = M_PI * x1;
xy.y = M_PI * sqrt(1. - x1 * (x1 + 2. * at) + TOL);
}
if ( lp.lam < 0.) xy.x = -xy.x;
if ( lp.phi < 0.) xy.y = -xy.y;
}
return xy;
}
PJ *PROJECTION(vandg2) {
struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
if (nullptr==Q)
return pj_default_destructor (P, ENOMEM);
P->opaque = Q;
Q->vdg3 = 0;
P->fwd = s_forward;
return P;
}
PJ *PROJECTION(vandg3) {
struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
if (nullptr==Q)
return pj_default_destructor (P, ENOMEM);
P->opaque = Q;
Q->vdg3 = 1;
P->es = 0.;
P->fwd = s_forward;
return P;
}
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