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static const char RCS_ID[] = "$Id: PJ_lcca.c 1504 2009-01-06 02:11:57Z warmerdam $";
/* PROJ.4 Cartographic Projection System
*/
#define MAX_ITER 10
#define DEL_TOL 1e-12
#define PROJ_PARMS__ \
double *en; \
double r0, l, M0; \
double C;
#define PJ_LIB__
#include <projects.h>
PROJ_HEAD(lcca, "Lambert Conformal Conic Alternative")
"\n\tConic, Sph&Ell\n\tlat_0=";
static double /* func to compute dr */
fS(double S, double C) {
return(S * ( 1. + S * S * C));
}
static double /* deriv of fs */
fSp(double S, double C) {
return(1. + 3.* S * S * C);
}
FORWARD(e_forward); /* ellipsoid */
double S, S3, r, dr;
S = pj_mlfn(lp.phi, sin(lp.phi), cos(lp.phi), P->en) - P->M0;
dr = fS(S, P->C);
r = P->r0 - dr;
xy.x = P->k0 * (r * sin( lp.lam *= P->l ) );
xy.y = P->k0 * (P->r0 - r * cos(lp.lam) );
return (xy);
}
INVERSE(e_inverse); /* ellipsoid & spheroid */
double theta, dr, S, dif;
int i;
xy.x /= P->k0;
xy.y /= P->k0;
theta = atan2(xy.x , P->r0 - xy.y);
dr = xy.y - xy.x * tan(0.5 * theta);
lp.lam = theta / P->l;
S = dr;
for (i = MAX_ITER; i ; --i) {
S -= (dif = (fS(S, P->C) - dr) / fSp(S, P->C));
if (fabs(dif) < DEL_TOL) break;
}
if (!i) I_ERROR
lp.phi = pj_inv_mlfn(S + P->M0, P->es, P->en);
return (lp);
}
FREEUP; if (P) { if (P->en) pj_dalloc(P->en); pj_dalloc(P); } }
ENTRY0(lcca)
double s2p0, N0, R0, tan0, tan20;
if (!(P->en = pj_enfn(P->es))) E_ERROR_0;
if (!pj_param(P->params, "tlat_0").i) E_ERROR(50);
if (P->phi0 == 0.) E_ERROR(51);
P->l = sin(P->phi0);
P->M0 = pj_mlfn(P->phi0, P->l, cos(P->phi0), P->en);
s2p0 = P->l * P->l;
R0 = 1. / (1. - P->es * s2p0);
N0 = sqrt(R0);
R0 *= P->one_es * N0;
tan0 = tan(P->phi0);
tan20 = tan0 * tan0;
P->r0 = N0 / tan0;
P->C = 1. / (6. * R0 * N0);
P->inv = e_inverse;
P->fwd = e_forward;
ENDENTRY(P)
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