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#define PJ_LIB__
#include <errno.h>
#include <math.h>
#include "projects.h"
PROJ_HEAD(wag3, "Wagner III") "\n\tPCyl, Sph\n\tlat_ts=";
#define TWOTHIRD 0.6666666666666666666667
struct pj_opaque {
double C_x;
};
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
xy.x = P->opaque->C_x * lp.lam * cos(TWOTHIRD * lp.phi);
xy.y = lp.phi;
return xy;
}
static LP s_inverse (XY xy, PJ *P) { /* Spheroidal, inverse */
LP lp = {0.0,0.0};
lp.phi = xy.y;
lp.lam = xy.x / (P->opaque->C_x * cos(TWOTHIRD * lp.phi));
return lp;
}
PJ *PROJECTION(wag3) {
double ts;
struct pj_opaque *Q = pj_calloc (1, sizeof (struct pj_opaque));
if (0==Q)
return pj_default_destructor(P, ENOMEM);
P->opaque = Q;
ts = pj_param (P->ctx, P->params, "rlat_ts").f;
P->opaque->C_x = cos (ts) / cos (2.*ts/3.);
P->es = 0.;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
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