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#define PJ_LIB__
#include <math.h>
#include "proj.h"
#include "proj_internal.h"
PROJ_HEAD(putp2, "Putnins P2") "\n\tPCyl, Sph";
#define C_x 1.89490
#define C_y 1.71848
#define C_p 0.6141848493043784
#define EPS 1e-10
#define NITER 10
#define PI_DIV_3 1.0471975511965977
static PJ_XY putp2_s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
PJ_XY xy = {0.0,0.0};
int i;
(void) P;
const double p = C_p * sin(lp.phi);
const double phi_pow_2 = lp.phi * lp.phi;
lp.phi *= 0.615709 + phi_pow_2 * ( 0.00909953 + phi_pow_2 * 0.0046292 );
for (i = NITER; i ; --i) {
const double c = cos(lp.phi);
const double s = sin(lp.phi);
const double V = (lp.phi + s * (c - 1.) - p) /
(1. + c * (c - 1.) - s * s);
lp.phi -= V;
if (fabs(V) < EPS)
break;
}
if (!i)
lp.phi = lp.phi < 0 ? - PI_DIV_3 : PI_DIV_3;
xy.x = C_x * lp.lam * (cos(lp.phi) - 0.5);
xy.y = C_y * sin(lp.phi);
return xy;
}
static PJ_LP putp2_s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
PJ_LP lp = {0.0,0.0};
lp.phi = aasin(P->ctx,xy.y / C_y);
const double c = cos(lp.phi);
lp.lam = xy.x / (C_x * (c - 0.5));
lp.phi = aasin(P->ctx,(lp.phi + sin(lp.phi) * (c - 1.)) / C_p);
return lp;
}
PJ *PROJECTION(putp2) {
P->es = 0.;
P->inv = putp2_s_inverse;
P->fwd = putp2_s_forward;
return P;
}
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