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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
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
double theta, th1, c;
int i;
(void) P;
theta = lp.phi;
if (fabs(fabs(lp.phi) - M_HALFPI) < EPS)
xy.x = 0.;
else {
c = sin(theta) * M_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 + M_SQRT2 * sin(theta));
return (xy);
}
static void *freeup_new (PJ *P) { /* Destructor */
return pj_dealloc(P);
}
static void freeup (PJ *P) {
freeup_new (P);
return;
}
PJ *PROJECTION(boggs) {
P->es = 0.;
P->fwd = s_forward;
return P;
}
#ifndef PJ_SELFTEST
int pj_boggs_selftest (void) {return 0;}
#else
int pj_boggs_selftest (void) {
double tolerance_lp = 1e-10;
double tolerance_xy = 1e-7;
char s_args[] = {"+proj=boggs +a=6400000 +lat_1=0 +lat_2=2"};
LP fwd_in[] = {
{ 2, 1},
{ 2,-1},
{-2, 1},
{-2,-1}
};
XY s_fwd_expect[] = {
{ 211949.70080818201, 117720.99830541089},
{ 211949.70080818201, -117720.99830541089},
{-211949.70080818201, 117720.99830541089},
{-211949.70080818201, -117720.99830541089},
};
return pj_generic_selftest (0, s_args, tolerance_xy, tolerance_lp, 4, 0, fwd_in, 0, s_fwd_expect, 0, 0, 0);
}
#endif
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