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| author | Frank Warmerdam <warmerdam@pobox.com> | 1999-03-18 16:34:52 +0000 |
|---|---|---|
| committer | Frank Warmerdam <warmerdam@pobox.com> | 1999-03-18 16:34:52 +0000 |
| commit | 565a4bd035b9d4a83955808efef20f1d8dfa24cf (patch) | |
| tree | 75785fc897708023f1ccdaf40079afcbaaf0fd3a /src/PJ_nell_h.c | |
| download | PROJ-565a4bd035b9d4a83955808efef20f1d8dfa24cf.tar.gz PROJ-565a4bd035b9d4a83955808efef20f1d8dfa24cf.zip | |
New
git-svn-id: http://svn.osgeo.org/metacrs/proj/trunk@776 4e78687f-474d-0410-85f9-8d5e500ac6b2
Diffstat (limited to 'src/PJ_nell_h.c')
| -rw-r--r-- | src/PJ_nell_h.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/src/PJ_nell_h.c b/src/PJ_nell_h.c new file mode 100644 index 00000000..3e87abec --- /dev/null +++ b/src/PJ_nell_h.c @@ -0,0 +1,33 @@ +#ifndef lint +static const char SCCSID[]="@(#)PJ_nell_h.c 4.1 94/02/15 GIE REL"; +#endif +#define PJ_LIB__ +# include <projects.h> +PROJ_HEAD(nell_h, "Nell-Hammer") "\n\tPCyl., Sph."; +#define NITER 9 +#define EPS 1e-7 +FORWARD(s_forward); /* spheroid */ + xy.x = 0.5 * lp.lam * (1. + cos(lp.phi)); + xy.y = 2.0 * (lp.phi - tan(0.5 *lp.phi)); + return (xy); +} +INVERSE(s_inverse); /* spheroid */ + double V, c, p; + int i; + + p = 0.5 * xy.y; + for (i = NITER; i ; --i) { + c = cos(0.5 * lp.phi); + lp.phi -= V = (lp.phi - tan(lp.phi/2) - p)/(1. - 0.5/(c*c)); + if (fabs(V) < EPS) + break; + } + if (!i) { + lp.phi = p < 0. ? -HALFPI : HALFPI; + lp.lam = 2. * xy.x; + } else + lp.lam = 2. * xy.x / (1. + cos(lp.phi)); + return (lp); +} +FREEUP; if (P) pj_dalloc(P); } +ENTRY0(nell_h) P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P) |