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#define PROJ_PARMS__ \
double qp; \
double *apa;
#define PJ_LIB__
# include <projects.h>
PROJ_HEAD(cea, "Equal Area Cylindrical") "\n\tCyl, Sph&Ell\n\tlat_ts=";
# define EPS 1e-10
FORWARD(e_forward); /* spheroid */
xy.x = P->k0 * lp.lam;
xy.y = .5 * pj_qsfn(sin(lp.phi), P->e, P->one_es) / P->k0;
return (xy);
}
FORWARD(s_forward); /* spheroid */
xy.x = P->k0 * lp.lam;
xy.y = sin(lp.phi) / P->k0;
return (xy);
}
INVERSE(e_inverse); /* spheroid */
lp.phi = pj_authlat(asin( 2. * xy.y * P->k0 / P->qp), P->apa);
lp.lam = xy.x / P->k0;
return (lp);
}
INVERSE(s_inverse); /* spheroid */
double t;
if ((t = fabs(xy.y *= P->k0)) - EPS <= 1.) {
if (t >= 1.)
lp.phi = xy.y < 0. ? -HALFPI : HALFPI;
else
lp.phi = asin(xy.y);
lp.lam = xy.x / P->k0;
} else I_ERROR;
return (lp);
}
FREEUP;
if (P) {
if (P->apa)
pj_dalloc(P->apa);
pj_dalloc(P);
}
}
ENTRY1(cea, apa)
double t;
if (pj_param(P->params, "tlat_ts").i &&
(P->k0 = cos(t = pj_param(P->params, "rlat_ts").f)) < 0.) E_ERROR(-24)
else
t = 0.;
if (P->es) {
t = sin(t);
P->k0 /= sqrt(1. - P->es * t * t);
P->e = sqrt(P->es);
if (!(P->apa = pj_authset(P->es))) E_ERROR_0;
P->qp = pj_qsfn(1., P->e, P->one_es);
P->inv = e_inverse;
P->fwd = e_forward;
} else {
P->inv = s_inverse;
P->fwd = s_forward;
}
ENDENTRY(P)
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