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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "proj.h"
#include "proj_internal.h"
PROJ_HEAD(gstmerc, "Gauss-Schreiber Transverse Mercator (aka Gauss-Laborde Reunion)")
"\n\tCyl, Sph&Ell\n\tlat_0= lon_0= k_0=";
namespace { // anonymous namespace
struct pj_opaque {
double lamc;
double phic;
double c;
double n1;
double n2;
double XS;
double YS;
};
} // anonymous namespace
static PJ_XY s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
PJ_XY xy = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double L, Ls, sinLs1, Ls1;
L = Q->n1*lp.lam;
Ls = Q->c + Q->n1 * log(pj_tsfn(-1.0 * lp.phi, -1.0 * sin(lp.phi), P->e));
sinLs1 = sin(L) / cosh(Ls);
Ls1 = log(pj_tsfn(-1.0 * asin(sinLs1), 0.0, 0.0));
xy.x = (Q->XS + Q->n2*Ls1) * P->ra;
xy.y = (Q->YS + Q->n2*atan(sinh(Ls) / cos(L))) * P->ra;
return xy;
}
static PJ_LP s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
PJ_LP lp = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double L, LC, sinC;
L = atan(sinh((xy.x * P->a - Q->XS) / Q->n2) / cos((xy.y * P->a - Q->YS) / Q->n2));
sinC = sin((xy.y * P->a - Q->YS) / Q->n2) / cosh((xy.x * P->a - Q->XS) / Q->n2);
LC = log(pj_tsfn(-1.0 * asin(sinC), 0.0, 0.0));
lp.lam = L / Q->n1;
lp.phi = -1.0 * pj_phi2(P->ctx, exp((LC - Q->c) / Q->n1), P->e);
return lp;
}
PJ *PROJECTION(gstmerc) {
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->lamc = P->lam0;
Q->n1 = sqrt(1.0 + P->es * pow(cos(P->phi0), 4.0) / (1.0 - P->es));
Q->phic = asin(sin(P->phi0) / Q->n1);
Q->c = log(pj_tsfn(-1.0 * Q->phic, 0.0, 0.0))
- Q->n1 * log(pj_tsfn(-1.0 * P->phi0, -1.0 * sin(P->phi0), P->e));
Q->n2 = P->k0 * P->a * sqrt(1.0 - P->es) / (1.0 - P->es * sin(P->phi0) * sin(P->phi0));
Q->XS = 0;
Q->YS = -1.0 * Q->n2 * Q->phic;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
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