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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "projects.h"
struct pj_opaque {
double C_x, C_y, A, B, D;
};
PROJ_HEAD(putp6, "Putnins P6") "\n\tPCyl, Sph";
PROJ_HEAD(putp6p, "Putnins P6'") "\n\tPCyl, Sph";
#define EPS 1e-10
#define NITER 10
#define CON_POLE 1.732050807568877
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
struct pj_opaque *Q = P->opaque;
double p, r, V;
int i;
p = Q->B * sin(lp.phi);
lp.phi *= 1.10265779;
for (i = NITER; i ; --i) {
r = sqrt(1. + lp.phi * lp.phi);
lp.phi -= V = ( (Q->A - r) * lp.phi - log(lp.phi + r) - p ) /
(Q->A - 2. * r);
if (fabs(V) < EPS)
break;
}
if (!i)
lp.phi = p < 0. ? -CON_POLE : CON_POLE;
xy.x = Q->C_x * lp.lam * (Q->D - sqrt(1. + lp.phi * lp.phi));
xy.y = Q->C_y * lp.phi;
return xy;
}
static LP s_inverse (XY xy, PJ *P) { /* Spheroidal, inverse */
LP lp = {0.0,0.0};
struct pj_opaque *Q = P->opaque;
double r;
lp.phi = xy.y / Q->C_y;
r = sqrt(1. + lp.phi * lp.phi);
lp.lam = xy.x / (Q->C_x * (Q->D - r));
lp.phi = aasin( P->ctx, ( (Q->A - r) * lp.phi - log(lp.phi + r) ) / Q->B);
return lp;
}
PJ *PROJECTION(putp6) {
struct pj_opaque *Q = pj_calloc (1, sizeof (struct pj_opaque));
if (0==Q)
return pj_default_destructor(P, ENOMEM);
P->opaque = Q;
Q->C_x = 1.01346;
Q->C_y = 0.91910;
Q->A = 4.;
Q->B = 2.1471437182129378784;
Q->D = 2.;
P->es = 0.;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
PJ *PROJECTION(putp6p) {
struct pj_opaque *Q = pj_calloc (1, sizeof (struct pj_opaque));
if (0==Q)
return pj_default_destructor(P, ENOMEM);
P->opaque = Q;
Q->C_x = 0.44329;
Q->C_y = 0.80404;
Q->A = 6.;
Q->B = 5.61125;
Q->D = 3.;
P->es = 0.;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
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