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#define PROJ_PARMS__ \
double C_x, C_y, A, B, D;
#define PJ_LIB__
#include <projects.h>
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
FORWARD(s_forward); /* spheroid */
double p, r, V;
int i;
p = P->B * sin(lp.phi);
lp.phi *= 1.10265779;
for (i = NITER; i ; --i) {
r = sqrt(1. + lp.phi * lp.phi);
lp.phi -= V = ( (P->A - r) * lp.phi - log(lp.phi + r) - p ) /
(P->A - 2. * r);
if (fabs(V) < EPS)
break;
}
if (!i)
lp.phi = p < 0. ? -CON_POLE : CON_POLE;
xy.x = P->C_x * lp.lam * (P->D - sqrt(1. + lp.phi * lp.phi));
xy.y = P->C_y * lp.phi;
return (xy);
}
INVERSE(s_inverse); /* spheroid */
double r;
lp.phi = xy.y / P->C_y;
r = sqrt(1. + lp.phi * lp.phi);
lp.lam = xy.x / (P->C_x * (P->D - r));
lp.phi = aasin( ( (P->A - r) * lp.phi - log(lp.phi + r) ) / P->B);
return (lp);
}
FREEUP; if (P) pj_dalloc(P); }
static PJ *
setup(PJ *P) {
P->es = 0.;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
ENTRY0(putp6)
P->C_x = 1.01346;
P->C_y = 0.91910;
P->A = 4.;
P->B = 2.1471437182129378784;
P->D = 2.;
ENDENTRY(setup(P))
ENTRY0(putp6p)
P->C_x = 0.44329;
P->C_y = 0.80404;
P->A = 6.;
P->B = 5.61125;
P->D = 3.;
ENDENTRY(setup(P))
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