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#define PJ_LIB__
# include <projects.h>
PROJ_HEAD(eck2, "Eckert II") "\n\tPCyl. Sph.";
#define FXC 0.46065886596178063902
#define FYC 1.44720250911653531871
#define C13 0.33333333333333333333
#define ONEEPS 1.0000001
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
(void) P;
xy.x = FXC * lp.lam * (xy.y = sqrt(4. - 3. * sin(fabs(lp.phi))));
xy.y = FYC * (2. - xy.y);
if ( lp.phi < 0.) xy.y = -xy.y;
return (xy);
}
static LP s_inverse (XY xy, PJ *P) { /* Spheroidal, inverse */
LP lp = {0.0,0.0};
(void) P;
lp.lam = xy.x / (FXC * ( lp.phi = 2. - fabs(xy.y) / FYC) );
lp.phi = (4. - lp.phi * lp.phi) * C13;
if (fabs(lp.phi) >= 1.) {
if (fabs(lp.phi) > ONEEPS) I_ERROR
else
lp.phi = lp.phi < 0. ? -M_HALFPI : M_HALFPI;
} else
lp.phi = asin(lp.phi);
if (xy.y < 0)
lp.phi = -lp.phi;
return (lp);
}
static void *freeup_new (PJ *P) { /* Destructor */
return pj_dealloc (P);
}
static void freeup (PJ *P) {
freeup_new (P);
return;
}
PJ *PROJECTION(eck2) {
P->es = 0.;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
#ifndef PJ_SELFTEST
int pj_eck2_selftest (void) {return 0;}
#else
int pj_eck2_selftest (void) {
double tolerance_lp = 1e-10;
double tolerance_xy = 1e-7;
char s_args[] = {"+proj=eck2 +a=6400000 +lat_1=0.5 +lat_2=2"};
LP fwd_in[] = {
{ 2, 1},
{ 2,-1},
{-2, 1},
{-2,-1}
};
XY s_fwd_expect[] = {
{ 204472.87090796008, 121633.73497524235},
{ 204472.87090796008, -121633.73497524235},
{-204472.87090796008, 121633.73497524235},
{-204472.87090796008, -121633.73497524235},
};
XY inv_in[] = {
{ 200, 100},
{ 200,-100},
{-200, 100},
{-200,-100}
};
LP s_inv_expect[] = {
{ 0.0019434150820034624, 0.00082480429919795412},
{ 0.0019434150820034624, -0.00082480429919795412},
{-0.0019434150820034624, 0.00082480429919795412},
{-0.0019434150820034624, -0.00082480429919795412},
};
return pj_generic_selftest (0, s_args, tolerance_xy, tolerance_lp, 4, 4, fwd_in, 0, s_fwd_expect, inv_in, 0, s_inv_expect);
}
#endif
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