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/*
** libproj -- library of cartographic projections
**
** Copyright (c) 2003 Gerald I. Evenden
*/
static const char
LIBPROJ_ID[] = "$Id: PJ_sterea.c 1504 2009-01-06 02:11:57Z warmerdam $";
/*
** Permission is hereby granted, free of charge, to any person obtaining
** a copy of this software and associated documentation files (the
** "Software"), to deal in the Software without restriction, including
** without limitation the rights to use, copy, modify, merge, publish,
** distribute, sublicense, and/or sell copies of the Software, and to
** permit persons to whom the Software is furnished to do so, subject to
** the following conditions:
**
** The above copyright notice and this permission notice shall be
** included in all copies or substantial portions of the Software.
**
** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#define PROJ_PARMS__ \
double phic0; \
double cosc0, sinc0; \
double R2; \
void *en;
#define PJ_LIB__
#include <projects.h>
PROJ_HEAD(sterea, "Oblique Stereographic Alternative")
"\n\tAzimuthal, Sph&Ell";
# define DEL_TOL 1.e-14
# define MAX_ITER 10
FORWARD(e_forward); /* ellipsoid */
double cosc, sinc, cosl, k;
lp = pj_gauss(lp, P->en);
sinc = sin(lp.phi);
cosc = cos(lp.phi);
cosl = cos(lp.lam);
k = P->k0 * P->R2 / (1. + P->sinc0 * sinc + P->cosc0 * cosc * cosl);
xy.x = k * cosc * sin(lp.lam);
xy.y = k * (P->cosc0 * sinc - P->sinc0 * cosc * cosl);
return (xy);
}
INVERSE(e_inverse); /* ellipsoid */
double rho, c, sinc, cosc;
xy.x /= P->k0;
xy.y /= P->k0;
if((rho = hypot(xy.x, xy.y))) {
c = 2. * atan2(rho, P->R2);
sinc = sin(c);
cosc = cos(c);
lp.phi = asin(cosc * P->sinc0 + xy.y * sinc * P->cosc0 / rho);
lp.lam = atan2(xy.x * sinc, rho * P->cosc0 * cosc -
xy.y * P->sinc0 * sinc);
} else {
lp.phi = P->phic0;
lp.lam = 0.;
}
return(pj_inv_gauss(lp, P->en));
}
FREEUP; if (P) { if (P->en) free(P->en); free(P); } }
ENTRY0(sterea)
double R;
if (!(P->en = pj_gauss_ini(P->e, P->phi0, &(P->phic0), &R))) E_ERROR_0;
P->sinc0 = sin(P->phic0);
P->cosc0 = cos(P->phic0);
P->R2 = 2. * R;
P->inv = e_inverse;
P->fwd = e_forward;
ENDENTRY(P)
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