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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "proj.h"
#include "projects.h"
PROJ_HEAD(somerc, "Swiss. Obl. Mercator") "\n\tCyl, Ell\n\tFor CH1903";
struct pj_opaque {
double K, c, hlf_e, kR, cosp0, sinp0;
};
#define EPS 1.e-10
#define NITER 6
static XY e_forward (LP lp, PJ *P) { /* Ellipsoidal, forward */
XY xy = {0.0, 0.0};
double phip, lamp, phipp, lampp, sp, cp;
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
sp = P->e * sin (lp.phi);
phip = 2.* atan ( exp ( Q->c * (
log (tan (M_FORTPI + 0.5 * lp.phi)) - Q->hlf_e * log ((1. + sp)/(1. - sp)))
+ Q->K)) - M_HALFPI;
lamp = Q->c * lp.lam;
cp = cos(phip);
phipp = aasin (P->ctx, Q->cosp0 * sin (phip) - Q->sinp0 * cp * cos (lamp));
lampp = aasin (P->ctx, cp * sin (lamp) / cos (phipp));
xy.x = Q->kR * lampp;
xy.y = Q->kR * log (tan (M_FORTPI + 0.5 * phipp));
return xy;
}
static LP e_inverse (XY xy, PJ *P) { /* Ellipsoidal, inverse */
LP lp = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double phip, lamp, phipp, lampp, cp, esp, con, delp;
int i;
phipp = 2. * (atan (exp (xy.y / Q->kR)) - M_FORTPI);
lampp = xy.x / Q->kR;
cp = cos (phipp);
phip = aasin (P->ctx, Q->cosp0 * sin (phipp) + Q->sinp0 * cp * cos (lampp));
lamp = aasin (P->ctx, cp * sin (lampp) / cos (phip));
con = (Q->K - log (tan (M_FORTPI + 0.5 * phip)))/Q->c;
for (i = NITER; i ; --i) {
esp = P->e * sin(phip);
delp = (con + log(tan(M_FORTPI + 0.5 * phip)) - Q->hlf_e *
log((1. + esp)/(1. - esp)) ) *
(1. - esp * esp) * cos(phip) * P->rone_es;
phip -= delp;
if (fabs(delp) < EPS)
break;
}
if (i) {
lp.phi = phip;
lp.lam = lamp / Q->c;
} else {
proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
return lp;
}
return (lp);
}
PJ *PROJECTION(somerc) {
double cp, phip0, sp;
struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
if (0==Q)
return pj_default_destructor (P, ENOMEM);
P->opaque = Q;
Q->hlf_e = 0.5 * P->e;
cp = cos (P->phi0);
cp *= cp;
Q->c = sqrt (1 + P->es * cp * cp * P->rone_es);
sp = sin (P->phi0);
Q->cosp0 = cos( phip0 = aasin (P->ctx, Q->sinp0 = sp / Q->c) );
sp *= P->e;
Q->K = log (tan (M_FORTPI + 0.5 * phip0)) - Q->c * (
log (tan (M_FORTPI + 0.5 * P->phi0)) - Q->hlf_e *
log ((1. + sp) / (1. - sp)));
Q->kR = P->k0 * sqrt(P->one_es) / (1. - sp * sp);
P->inv = e_inverse;
P->fwd = e_forward;
return P;
}
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