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#define PJ_LIB__
#include <math.h>
#include "proj.h"
#include "projects.h"
PROJ_HEAD(mbtfpp, "McBride-Thomas Flat-Polar Parabolic") "\n\tCyl, Sph";
#define CS .95257934441568037152
#define FXC .92582009977255146156
#define FYC 3.40168025708304504493
#define C23 .66666666666666666666
#define C13 .33333333333333333333
#define ONEEPS 1.0000001
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
(void) P;
lp.phi = asin(CS * sin(lp.phi));
xy.x = FXC * lp.lam * (2. * cos(C23 * lp.phi) - 1.);
xy.y = FYC * sin(C13 * lp.phi);
return xy;
}
static LP s_inverse (XY xy, PJ *P) { /* Spheroidal, inverse */
LP lp = {0.0,0.0};
lp.phi = xy.y / FYC;
if (fabs(lp.phi) >= 1.) {
if (fabs(lp.phi) > ONEEPS) {
proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
return lp;
} else {
lp.phi = (lp.phi < 0.) ? -M_HALFPI : M_HALFPI;
}
} else
lp.phi = asin(lp.phi);
lp.lam = xy.x / ( FXC * (2. * cos(C23 * (lp.phi *= 3.)) - 1.) );
if (fabs(lp.phi = sin(lp.phi) / CS) >= 1.) {
if (fabs(lp.phi) > ONEEPS) {
proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
return lp;
} else {
lp.phi = (lp.phi < 0.) ? -M_HALFPI : M_HALFPI;
}
} else
lp.phi = asin(lp.phi);
return lp;
}
PJ *PROJECTION(mbtfpp) {
P->es = 0.;
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
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