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#define PJ_LIB__
#include <projects.h>
PROJ_HEAD(mbt_fps, "McBryde-Thomas Flat-Pole Sine (No. 2)") "\n\tCyl., Sph.";
#define MAX_ITER 10
#define LOOP_TOL 1e-7
#define C1 0.45503
#define C2 1.36509
#define C3 1.41546
#define C_x 0.22248
#define C_y 1.44492
#define C1_2 0.33333333333333333333333333
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
double k, V, t;
int i;
(void) P;
k = C3 * sin(lp.phi);
for (i = MAX_ITER; i ; --i) {
t = lp.phi / C2;
lp.phi -= V = (C1 * sin(t) + sin(lp.phi) - k) /
(C1_2 * cos(t) + cos(lp.phi));
if (fabs(V) < LOOP_TOL)
break;
}
t = lp.phi / C2;
xy.x = C_x * lp.lam * (1. + 3. * cos(lp.phi)/cos(t) );
xy.y = C_y * sin(t);
return xy;
}
static LP s_inverse (XY xy, PJ *P) { /* Spheroidal, inverse */
LP lp = {0.0,0.0};
double t;
lp.phi = C2 * (t = aasin(P->ctx,xy.y / C_y));
lp.lam = xy.x / (C_x * (1. + 3. * cos(lp.phi)/cos(t)));
lp.phi = aasin(P->ctx,(C1 * sin(t) + sin(lp.phi)) / C3);
return (lp);
}
static void *freeup_new (PJ *P) { /* Destructor */
if (0==P)
return 0;
return pj_dealloc(P);
}
static void freeup (PJ *P) {
freeup_new (P);
return;
}
PJ *PROJECTION(mbt_fps) {
P->es = 0;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
#ifndef PJ_SELFTEST
int pj_mbt_fps_selftest (void) {return 0;}
#else
int pj_mbt_fps_selftest (void) {
double tolerance_lp = 1e-10;
double tolerance_xy = 1e-7;
char s_args[] = {"+proj=mbt_fps +a=6400000 +lat_1=0.5 +lat_2=2"};
LP fwd_in[] = {
{ 2, 1},
{ 2,-1},
{-2, 1},
{-2,-1}
};
XY s_fwd_expect[] = {
{ 198798.176129849948, 125512.017254530627},
{ 198798.176129849948, -125512.017254530627},
{-198798.176129849948, 125512.017254530627},
{-198798.176129849948, -125512.017254530627},
};
XY inv_in[] = {
{ 200, 100},
{ 200,-100},
{-200, 100},
{-200,-100}
};
LP s_inv_expect[] = {
{ 0.00201197086238270742, 0.000796711850174446003},
{ 0.00201197086238270742, -0.000796711850174446003},
{-0.00201197086238270742, 0.000796711850174446003},
{-0.00201197086238270742, -0.000796711850174446003},
};
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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