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#define PJ_LIB__
# include <projects.h>
PROJ_HEAD(boggs, "Boggs Eumorphic") "\n\tPCyl., no inv., Sph.";
# define NITER 20
# define EPS 1e-7
# define ONETOL 1.000001
# define FXC 2.00276
# define FXC2 1.11072
# define FYC 0.49931
# define FYC2 1.41421356237309504880
FORWARD(s_forward); /* spheroid */
double theta, th1, c;
int i;
theta = lp.phi;
if (fabs(fabs(lp.phi) - HALFPI) < EPS)
xy.x = 0.;
else {
c = sin(theta) * PI;
for (i = NITER; i; --i) {
theta -= th1 = (theta + sin(theta) - c) /
(1. + cos(theta));
if (fabs(th1) < EPS) break;
}
theta *= 0.5;
xy.x = FXC * lp.lam / (1. / cos(lp.phi) + FXC2 / cos(theta));
}
xy.y = FYC * (lp.phi + FYC2 * sin(theta));
return (xy);
}
FREEUP; if (P) pj_dalloc(P); }
ENTRY0(boggs) P->es = 0.; P->fwd = s_forward; ENDENTRY(P)
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