PJ_ortho.c
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#define PROJ_PARMS__ \
double sinph0; \
double cosph0; \
int mode;
#define PJ_LIB__
#include <projects.h>
PROJ_HEAD(ortho, "Orthographic") "\n\tAzi, Sph.";
#define EPS10 1.e-10
#define N_POLE 0
#define S_POLE 1
#define EQUIT 2
#define OBLIQ 3
FORWARD(s_forward); /* spheroid */
double coslam, cosphi, sinphi;
cosphi = cos(lp.phi);
coslam = cos(lp.lam);
switch (P->mode) {
case EQUIT:
if (cosphi * coslam < - EPS10) F_ERROR;
xy.y = sin(lp.phi);
break;
case OBLIQ:
if (P->sinph0 * (sinphi = sin(lp.phi)) +
P->cosph0 * cosphi * coslam < - EPS10) F_ERROR;
xy.y = P->cosph0 * sinphi - P->sinph0 * cosphi * coslam;
break;
case N_POLE:
coslam = - coslam;
case S_POLE:
if (fabs(lp.phi - P->phi0) - EPS10 > HALFPI) F_ERROR;
xy.y = cosphi * coslam;
break;
}
xy.x = cosphi * sin(lp.lam);
return (xy);
}
INVERSE(s_inverse); /* spheroid */
double rh, cosc, sinc;
if ((sinc = (rh = hypot(xy.x, xy.y))) > 1.) {
if ((sinc - 1.) > EPS10) I_ERROR;
sinc = 1.;
}
cosc = sqrt(1. - sinc * sinc); /* in this range OK */
if (fabs(rh) <= EPS10) {
lp.phi = P->phi0;
lp.lam = 0.0;
} else {
switch (P->mode) {
case N_POLE:
xy.y = -xy.y;
lp.phi = acos(sinc);
break;
case S_POLE:
lp.phi = - acos(sinc);
break;
case EQUIT:
lp.phi = xy.y * sinc / rh;
xy.x *= sinc;
xy.y = cosc * rh;
goto sinchk;
case OBLIQ:
lp.phi = cosc * P->sinph0 + xy.y * sinc * P->cosph0 /rh;
xy.y = (cosc - P->sinph0 * lp.phi) * rh;
xy.x *= sinc * P->cosph0;
sinchk:
if (fabs(lp.phi) >= 1.)
lp.phi = lp.phi < 0. ? -HALFPI : HALFPI;
else
lp.phi = asin(lp.phi);
break;
}
lp.lam = (xy.y == 0. && (P->mode == OBLIQ || P->mode == EQUIT))
? (xy.x == 0. ? 0. : xy.x < 0. ? -HALFPI : HALFPI)
: atan2(xy.x, xy.y);
}
return (lp);
}
FREEUP; if (P) pj_dalloc(P); }
ENTRY0(ortho)
if (fabs(fabs(P->phi0) - HALFPI) <= EPS10)
P->mode = P->phi0 < 0. ? S_POLE : N_POLE;
else if (fabs(P->phi0) > EPS10) {
P->mode = OBLIQ;
P->sinph0 = sin(P->phi0);
P->cosph0 = cos(P->phi0);
} else
P->mode = EQUIT;
P->inv = s_inverse;
P->fwd = s_forward;
P->es = 0.;
ENDENTRY(P)