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#define PJ_LIB__
#include <errno.h>
#include <proj.h>
#include "projects.h"
PROJ_HEAD(lagrng, "Lagrange") "\n\tMisc Sph, no inv.\n\tW=";
#define TOL 1e-10
struct pj_opaque {
double a1;
double hrw;
double rw;
};
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
struct pj_opaque *Q = P->opaque;
double v, c;
if (fabs(fabs(lp.phi) - M_HALFPI) < TOL) {
xy.x = 0;
xy.y = lp.phi < 0 ? -2. : 2.;
} else {
lp.phi = sin(lp.phi);
v = Q->a1 * pow((1. + lp.phi)/(1. - lp.phi), Q->hrw);
if ((c = 0.5 * (v + 1./v) + cos(lp.lam *= Q->rw)) < TOL) {
proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
return xy;
}
xy.x = 2. * sin(lp.lam) / c;
xy.y = (v - 1./v) / c;
}
return xy;
}
PJ *PROJECTION(lagrng) {
double phi1;
struct pj_opaque *Q = pj_calloc (1, sizeof (struct pj_opaque));
if (0==Q)
return pj_default_destructor (P, ENOMEM);
P->opaque = Q;
Q->rw = pj_param(P->ctx, P->params, "dW").f;
if (Q->rw <= 0)
return pj_default_destructor(P, PJD_ERR_W_OR_M_ZERO_OR_LESS);
Q->rw = 1. / Q->rw;
Q->hrw = 0.5 * Q->rw;
phi1 = sin(pj_param(P->ctx, P->params, "rlat_1").f);
if (fabs(fabs(phi1) - 1.) < TOL)
return pj_default_destructor(P, PJD_ERR_LAT_LARGER_THAN_90);
Q->a1 = pow((1. - phi1)/(1. + phi1), Q->hrw);
P->es = 0.;
P->fwd = s_forward;
return P;
}
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