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/*
** libproj -- library of cartographic projections
**
** Copyright (c) 2003, 2006 Gerald I. Evenden
*/
static const char
LIBPROJ_ID[] = "Id";
/*
** Permission is hereby granted, free of charge, to any person obtaining
** a copy of this software and associated documentation files (the
** "Software"), to deal in the Software without restriction, including
** without limitation the rights to use, copy, modify, merge, publish,
** distribute, sublicense, and/or sell copies of the Software, and to
** permit persons to whom the Software is furnished to do so, subject to
** the following conditions:
**
** The above copyright notice and this permission notice shall be
** included in all copies or substantial portions of the Software.
**
** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
# define TOL 1e-10
# define TWORPI 0.63661977236758134308
#define PROJ_PARMS__ \
int vdg3;
#define PROJ_LIB__
#include <lib_proj.h>
PROJ_HEAD(vandg2, "van der Grinten II") "\n\tMisc Sph, no inv.";
PROJ_HEAD(vandg3, "van der Grinten III") "\n\tMisc Sph, no inv.";
FORWARD(s_forward); /* spheroid */
double x1, at, bt, ct;
bt = fabs(TWORPI * lp.phi);
if ((ct = 1. - bt * bt) < 0.)
ct = 0.;
else
ct = sqrt(ct);
if (fabs(lp.lam) < TOL) {
xy.x = 0.;
xy.y = PI * (lp.phi < 0. ? -bt : bt) / (1. + ct);
} else {
at = 0.5 * fabs(PI / lp.lam - lp.lam / PI);
if (P->vdg3) {
x1 = bt / (1. + ct);
xy.x = PI * (sqrt(fabs(at * at + 1. - x1 * x1)) - at);
xy.y = PI * x1;
} else {
x1 = (ct * sqrt(1. + at * at) - at * ct * ct) /
(1. + at * at * bt * bt);
xy.x = PI * x1;
xy.y = PI * sqrt(1. - x1 * (x1 + 2. * at) + TOL);
}
if ( lp.lam < 0.) xy.x = -xy.x;
if ( lp.phi < 0.) xy.y = -xy.y;
}
return (xy);
}
FREEUP; if (P) free(P); }
ENTRY0(vandg2)
P->vdg3 = 0;
P->es = 0.; P->fwd = s_forward;
ENDENTRY(P)
ENTRY0(vandg3)
P->vdg3 = 1;
P->es = 0.; P->fwd = s_forward;
ENDENTRY(P)
/*
** Log: proj_vandg2.c
** Revision 3.1 2006/01/11 01:38:18 gie
** Initial
**
*/
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