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#define PJ_LIB__
#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)
F_ERROR;
xy.x = 2. * sin(lp.lam) / c;
xy.y = (v - 1./v) / c;
}
return xy;
}
static void *freeup_new (PJ *P) { /* Destructor */
if (0==P)
return 0;
if (0==P->opaque)
return pj_dealloc (P);
pj_dealloc (P->opaque);
return pj_dealloc(P);
}
static void freeup (PJ *P) {
freeup_new (P);
return;
}
PJ *PROJECTION(lagrng) {
double phi1;
struct pj_opaque *Q = pj_calloc (1, sizeof (struct pj_opaque));
if (0==Q)
return freeup_new (P);
P->opaque = Q;
Q->rw = pj_param(P->ctx, P->params, "dW").f;
if (Q->rw <= 0) E_ERROR(-27);
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) E_ERROR(-22);
Q->a1 = pow((1. - phi1)/(1. + phi1), Q->hrw);
P->es = 0.;
P->fwd = s_forward;
return P;
}
#ifndef PJ_SELFTEST
int pj_lagrng_selftest (void) {return 0;}
#else
int pj_lagrng_selftest (void) {
double tolerance_lp = 1e-10;
double tolerance_xy = 1e-7;
char s_args[] = {"+proj=lagrng +a=6400000 +W=2 +lat_1=0.5 +lat_2=2"};
LP fwd_in[] = {
{ 2, 1},
{ 2,-1},
{-2, 1},
{-2,-1}
};
XY s_fwd_expect[] = {
{ 111703.37591722561, 27929.8319080333386},
{ 111699.122088816002, -83784.1780133577704},
{-111703.37591722561, 27929.8319080333386},
{-111699.122088816002, -83784.1780133577704},
};
return pj_generic_selftest (0, s_args, tolerance_xy, tolerance_lp, 4, 4, fwd_in, 0, s_fwd_expect, 0, 0, 0);
}
#endif
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