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#define PROJ_PARMS__ \
double C_x, C_y, C_p;
#define PJ_LIB__
#include <projects.h>
PROJ_HEAD(moll, "Mollweide") "\n\tPCyl., Sph.";
PROJ_HEAD(wag4, "Wagner IV") "\n\tPCyl., Sph.";
PROJ_HEAD(wag5, "Wagner V") "\n\tPCyl., Sph.";
#define MAX_ITER 10
#define LOOP_TOL 1e-7
FORWARD(s_forward); /* spheroid */
double k, V;
int i;
k = P->C_p * sin(lp.phi);
for (i = MAX_ITER; i ; --i) {
lp.phi -= V = (lp.phi + sin(lp.phi) - k) /
(1. + cos(lp.phi));
if (fabs(V) < LOOP_TOL)
break;
}
if (!i)
lp.phi = (lp.phi < 0.) ? -HALFPI : HALFPI;
else
lp.phi *= 0.5;
xy.x = P->C_x * lp.lam * cos(lp.phi);
xy.y = P->C_y * sin(lp.phi);
return (xy);
}
INVERSE(s_inverse); /* spheroid */
double th, s;
lp.phi = aasin(xy.y / P->C_y);
lp.lam = xy.x / (P->C_x * cos(lp.phi));
lp.phi += lp.phi;
lp.phi = aasin((lp.phi + sin(lp.phi)) / P->C_p);
return (lp);
}
FREEUP; if (P) pj_dalloc(P); }
static PJ *
setup(PJ *P, double p) {
double r, sp, p2 = p + p;
P->es = 0;
sp = sin(p);
r = sqrt(TWOPI * sp / (p2 + sin(p2)));
P->C_x = 2. * r / PI;
P->C_y = r / sp;
P->C_p = p2 + sin(p2);
P->inv = s_inverse;
P->fwd = s_forward;
return P;
}
ENTRY0(moll) ENDENTRY(setup(P, HALFPI))
ENTRY0(wag4) ENDENTRY(setup(P, PI/3.))
ENTRY0(wag5)
P->es = 0;
P->C_x = 0.90977;
P->C_y = 1.65014;
P->C_p = 3.00896;
P->inv = s_inverse;
P->fwd = s_forward;
ENDENTRY(P)
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