/Proj4/PJ_mbtfpq.c
http://github.com/route-me/route-me · C · 50 lines · 48 code · 2 blank · 0 comment · 10 complexity · 07b0ecb3ae08242322f67b5cb32108b4 MD5 · raw file
- #ifndef lint
- static const char SCCSID[]="@(#)PJ_mbtfpq.c 4.1 94/02/15 GIE REL";
- #endif
- #define PJ_LIB__
- #include "projects.h"
- PROJ_HEAD(mbtfpq, "McBryde-Thomas Flat-Polar Quartic") "\n\tCyl., Sph.";
- #define NITER 20
- #define EPS 1e-7
- #define ONETOL 1.000001
- #define C 1.70710678118654752440
- #define RC 0.58578643762690495119
- #define FYC 1.87475828462269495505
- #define RYC 0.53340209679417701685
- #define FXC 0.31245971410378249250
- #define RXC 3.20041258076506210122
- FORWARD(s_forward); /* spheroid */
- double th1, c;
- int i;
- c = C * sin(lp.phi);
- for (i = NITER; i; --i) {
- lp.phi -= th1 = (sin(.5*lp.phi) + sin(lp.phi) - c) /
- (.5*cos(.5*lp.phi) + cos(lp.phi));
- if (fabs(th1) < EPS) break;
- }
- xy.x = FXC * lp.lam * (1.0 + 2. * cos(lp.phi)/cos(0.5 * lp.phi));
- xy.y = FYC * sin(0.5 * lp.phi);
- return (xy);
- }
- INVERSE(s_inverse); /* spheroid */
- double t;
- lp.phi = RYC * xy.y;
- if (fabs(lp.phi) > 1.) {
- if (fabs(lp.phi) > ONETOL) I_ERROR
- else if (lp.phi < 0.) { t = -1.; lp.phi = -PI; }
- else { t = 1.; lp.phi = PI; }
- } else
- lp.phi = 2. * asin(t = lp.phi);
- lp.lam = RXC * xy.x / (1. + 2. * cos(lp.phi)/cos(0.5 * lp.phi));
- lp.phi = RC * (t + sin(lp.phi));
- if (fabs(lp.phi) > 1.)
- if (fabs(lp.phi) > ONETOL) I_ERROR
- else lp.phi = lp.phi < 0. ? -HALFPI : HALFPI;
- else
- lp.phi = asin(lp.phi);
- return (lp);
- }
- FREEUP; if (P) pj_dalloc(P); }
- ENTRY0(mbtfpq) P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P)