/Proj4/PJ_sterea.c

 1/*
 2** libproj -- library of cartographic projections
 3**
 4** Copyright (c) 2003   Gerald I. Evenden
 5*/
 6static const char
 7LIBPROJ_ID[] = "$Id: PJ_sterea.c,v 1.1 2004/10/20 17:04:00 fwarmerdam Exp $";
 8/*
 9** Permission is hereby granted, free of charge, to any person obtaining
10** a copy of this software and associated documentation files (the
11** "Software"), to deal in the Software without restriction, including
12** without limitation the rights to use, copy, modify, merge, publish,
13** distribute, sublicense, and/or sell copies of the Software, and to
14** permit persons to whom the Software is furnished to do so, subject to
15** the following conditions:
16**
17** The above copyright notice and this permission notice shall be
18** included in all copies or substantial portions of the Software.
19**
20** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
23** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
24** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
25** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
26** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
27*/
28#define PROJ_PARMS__ \
29	double phic0; \
30	double cosc0, sinc0; \
31	double R2; \
32	void *en;
33
34#define PJ_LIB__
35#include	"projects.h"
36
37PROJ_HEAD(sterea, "Oblique Stereographic Alternative")
38	"\n\tAzimuthal, Sph&Ell";
39# define DEL_TOL	1.e-14
40# define MAX_ITER	10
41
42FORWARD(e_forward); /* ellipsoid */
43	double cosc, sinc, cosl, k;
44
45	lp = pj_gauss(lp, P->en);
46	sinc = sin(lp.phi);
47	cosc = cos(lp.phi);
48	cosl = cos(lp.lam);
49	k = P->k0 * P->R2 / (1. + P->sinc0 * sinc + P->cosc0 * cosc * cosl);
50	xy.x = k * cosc * sin(lp.lam);
51	xy.y = k * (P->cosc0 * sinc - P->sinc0 * cosc * cosl);
52	return (xy);
53}
54INVERSE(e_inverse); /* ellipsoid */
55	double rho, c, sinc, cosc;
56
57	xy.x /= P->k0;
58	xy.y /= P->k0;
59	if((rho = hypot(xy.x, xy.y))) {
60		c = 2. * atan2(rho, P->R2);
61		sinc = sin(c);
62		cosc = cos(c);
63		lp.phi = asin(cosc * P->sinc0 + xy.y * sinc * P->cosc0 / rho);
64		lp.lam = atan2(xy.x * sinc, rho * P->cosc0 * cosc -
65			xy.y * P->sinc0 * sinc);
66	} else {
67		lp.phi = P->phic0;
68		lp.lam = 0.;
69	}
70	return(pj_inv_gauss(lp, P->en));
71}
72FREEUP; if (P) { if (P->en) free(P->en); free(P); } }
73ENTRY0(sterea)
74	double R;
75
76	if (!(P->en = pj_gauss_ini(P->e, P->phi0, &(P->phic0), &R))) E_ERROR_0;
77	P->sinc0 = sin(P->phic0);
78	P->cosc0 = cos(P->phic0);
79	P->R2 = 2. * R;
80	P->inv = e_inverse;
81	P->fwd = e_forward;
82ENDENTRY(P)
83/*
84** $Log: PJ_sterea.c,v $
85** Revision 1.1  2004/10/20 17:04:00  fwarmerdam
86** New
87**
88** Revision 2.3  2004/04/07 17:18:32  gie
89** corrected comment stamp
90**
91** Revision 2.2  2003/08/05 00:15:09  gie
92** corrected 0 rho on inverse.
93**
94** Revision 2.1  2003/03/28 01:46:02  gie
95** Initial
96**
97*/