diff options
Diffstat (limited to 'src/3rdparty/proj/PJ_vandg4.c')
| -rw-r--r-- | src/3rdparty/proj/PJ_vandg4.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/src/3rdparty/proj/PJ_vandg4.c b/src/3rdparty/proj/PJ_vandg4.c new file mode 100644 index 00000000..d6705031 --- /dev/null +++ b/src/3rdparty/proj/PJ_vandg4.c @@ -0,0 +1,41 @@ +#define PJ_LIB__ +#include <projects.h> +PROJ_HEAD(vandg4, "van der Grinten IV") "\n\tMisc Sph, no inv."; +#define TOL 1e-10 +#define TWORPI 0.63661977236758134308 +FORWARD(s_forward); /* spheroid */ + double x1, t, bt, ct, ft, bt2, ct2, dt, dt2; + + if (fabs(lp.phi) < TOL) { + xy.x = lp.lam; + xy.y = 0.; + } else if (fabs(lp.lam) < TOL || fabs(fabs(lp.phi) - HALFPI) < TOL) { + xy.x = 0.; + xy.y = lp.phi; + } else { + bt = fabs(TWORPI * lp.phi); + bt2 = bt * bt; + ct = 0.5 * (bt * (8. - bt * (2. + bt2)) - 5.) + / (bt2 * (bt - 1.)); + ct2 = ct * ct; + dt = TWORPI * lp.lam; + dt = dt + 1. / dt; + dt = sqrt(dt * dt - 4.); + if ((fabs(lp.lam) - HALFPI) < 0.) dt = -dt; + dt2 = dt * dt; + x1 = bt + ct; x1 *= x1; + t = bt + 3.*ct; + ft = x1 * (bt2 + ct2 * dt2 - 1.) + (1.-bt2) * ( + bt2 * (t * t + 4. * ct2) + + ct2 * (12. * bt * ct + 4. * ct2) ); + x1 = (dt*(x1 + ct2 - 1.) + 2.*sqrt(ft)) / + (4.* x1 + dt2); + xy.x = HALFPI * x1; + xy.y = HALFPI * sqrt(1. + dt * fabs(x1) - x1 * x1); + if (lp.lam < 0.) xy.x = -xy.x; + if (lp.phi < 0.) xy.y = -xy.y; + } + return (xy); +} +FREEUP; if (P) pj_dalloc(P); } +ENTRY0(vandg4) P->es = 0.; P->fwd = s_forward; ENDENTRY(P) |