/Proj4/PJ_lcca.c

 1static const char RCS_ID[] = "$Id: PJ_lcca.c,v 1.1 2003/03/04 02:59:41 warmerda Exp $";
 2/* PROJ.4 Cartographic Projection System -- Revision Log:
 3**$Log: PJ_lcca.c,v $
 4**Revision 1.1  2003/03/04 02:59:41  warmerda
 5**New
 6**
 7*/
 8#define MAX_ITER 10
 9#define DEL_TOL 1e-12
10#define PROJ_PARMS__ \
11	double	*en; \
12	double	r0, l, M0; \
13	double	C;
14#define PJ_LIB__
15#include	"projects.h"
16
17PROJ_HEAD(lcca, "Lambert Conformal Conic Alternative")
18	"\n\tConic, Sph&Ell\n\tlat_0=";
19
20	static double /* func to compute dr */
21fS(double S, double C) {
22		return(S * ( 1. + S * S * C));
23}
24	static double /* deriv of fs */
25fSp(double S, double C) {
26	return(1. + 3.* S * S * C);
27}
28FORWARD(e_forward); /* ellipsoid */
29	double S, S3, r, dr;
30	
31	S = pj_mlfn(lp.phi, sin(lp.phi), cos(lp.phi), P->en) - P->M0;
32	dr = fS(S, P->C);
33	r = P->r0 - dr;
34	xy.x = P->k0 * (r * sin( lp.lam *= P->l ) );
35	xy.y = P->k0 * (P->r0 - r * cos(lp.lam) );
36	return (xy);
37}
38INVERSE(e_inverse); /* ellipsoid & spheroid */
39	double theta, dr, S, dif;
40	int i;
41
42	xy.x /= P->k0;
43	xy.y /= P->k0;
44	theta = atan2(xy.x , P->r0 - xy.y);
45	dr = xy.y - xy.x * tan(0.5 * theta);
46	lp.lam = theta / P->l;
47	S = dr;
48	for (i = MAX_ITER; i ; --i) {
49		S -= (dif = (fS(S, P->C) - dr) / fSp(S, P->C));
50		if (fabs(dif) < DEL_TOL) break;
51	}
52	if (!i) I_ERROR
53	lp.phi = pj_inv_mlfn(S + P->M0, P->es, P->en);
54	return (lp);
55}
56FREEUP; if (P) { if (P->en) pj_dalloc(P->en); pj_dalloc(P); } }
57ENTRY0(lcca)
58	double s2p0, N0, R0, tan0, tan20;
59
60	if (!(P->en = pj_enfn(P->es))) E_ERROR_0;
61	if (!pj_param(P->params, "tlat_0").i) E_ERROR(50);
62	if (P->phi0 == 0.) E_ERROR(51);
63	P->l = sin(P->phi0);
64	P->M0 = pj_mlfn(P->phi0, P->l, cos(P->phi0), P->en);
65	s2p0 = P->l * P->l;
66	R0 = 1. / (1. - P->es * s2p0);
67	N0 = sqrt(R0);
68	R0 *= P->one_es * N0;
69	tan0 = tan(P->phi0);
70	tan20 = tan0 * tan0;
71	P->r0 = N0 / tan0;
72	P->C = 1. / (6. * R0 * N0);
73	P->inv = e_inverse;
74	P->fwd = e_forward;
75ENDENTRY(P)
76