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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "proj.h"
#include "proj_internal.h"
PROJ_HEAD(fouc_s, "Foucaut Sinusoidal") "\n\tPCyl, Sph";
#define MAX_ITER 10
#define LOOP_TOL 1e-7
namespace { // anonymous namespace
struct pj_opaque {
double n, n1;
};
} // anonymous namespace
static PJ_XY fouc_s_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 t;
t = cos(lp.phi);
xy.x = lp.lam * t / (Q->n + Q->n1 * t);
xy.y = Q->n * lp.phi + Q->n1 * sin(lp.phi);
return xy;
}
static PJ_LP fouc_s_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);
int i;
if (Q->n != 0.0) {
lp.phi = xy.y;
for (i = MAX_ITER; i ; --i) {
const double V = (Q->n * lp.phi + Q->n1 * sin(lp.phi) - xy.y ) /
(Q->n + Q->n1 * cos(lp.phi));
lp.phi -= V;
if (fabs(V) < LOOP_TOL)
break;
}
if (!i)
lp.phi = xy.y < 0. ? -M_HALFPI : M_HALFPI;
} else
lp.phi = aasin(P->ctx,xy.y);
const double V = cos(lp.phi);
lp.lam = xy.x * (Q->n + Q->n1 * V) / V;
return lp;
}
PJ *PROJECTION(fouc_s) {
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->n = pj_param(P->ctx, P->params, "dn").f;
if (Q->n < 0. || Q->n > 1.)
return pj_default_destructor (P, PJD_ERR_N_OUT_OF_RANGE);
Q->n1 = 1. - Q->n;
P->es = 0;
P->inv = fouc_s_s_inverse;
P->fwd = fouc_s_s_forward;
return P;
}
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