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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "proj.h"
#include "projects.h"
PROJ_HEAD(hammer, "Hammer & Eckert-Greifendorff")
"\n\tMisc Sph, \n\tW= M=";
#define EPS 1.0e-10
namespace { // anonymous namespace
struct pj_opaque {
double w;
double m, rm;
};
} // anonymous namespace
static PJ_XY s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
PJ_XY xy = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double cosphi, d;
d = sqrt(2./(1. + (cosphi = cos(lp.phi)) * cos(lp.lam *= Q->w)));
xy.x = Q->m * d * cosphi * sin(lp.lam);
xy.y = Q->rm * d * sin(lp.phi);
return xy;
}
static PJ_LP s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
PJ_LP lp = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double z;
z = sqrt(1. - 0.25*Q->w*Q->w*xy.x*xy.x - 0.25*xy.y*xy.y);
if (fabs(2.*z*z-1.) < EPS) {
lp.lam = HUGE_VAL;
lp.phi = HUGE_VAL;
proj_errno_set(P, PJD_ERR_LAT_OR_LON_EXCEED_LIMIT);
} else {
lp.lam = aatan2(Q->w * xy.x * z,2. * z * z - 1)/Q->w;
lp.phi = aasin(P->ctx,z * xy.y);
}
return lp;
}
PJ *PROJECTION(hammer) {
struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
if (nullptr==Q)
return pj_default_destructor (P, ENOMEM);
P->opaque = Q;
if (pj_param(P->ctx, P->params, "tW").i) {
if ((Q->w = fabs(pj_param(P->ctx, P->params, "dW").f)) <= 0.)
return pj_default_destructor (P, PJD_ERR_W_OR_M_ZERO_OR_LESS);
} else
Q->w = .5;
if (pj_param(P->ctx, P->params, "tM").i) {
if ((Q->m = fabs(pj_param(P->ctx, P->params, "dM").f)) <= 0.)
return pj_default_destructor (P, PJD_ERR_W_OR_M_ZERO_OR_LESS);
} else
Q->m = 1.;
Q->rm = 1. / Q->m;
Q->m /= Q->w;
P->es = 0.;
P->fwd = s_forward;
P->inv = s_inverse;
return P;
}
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