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[r5435]: / trunk / toolkits / basemap / src / PJ_eck2.c  Maximize  Restore  History

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#ifndef lint
static const char SCCSID[]="@(#)PJ_eck2.c 4.1 94/02/15 GIE REL";
#endif
#define PJ_LIB__
# include <projects.h>
PROJ_HEAD(eck2, "Eckert II") "\n\tPCyl. Sph.";
#define FXC 0.46065886596178063902
#define FYC 1.44720250911653531871
#define C13 0.33333333333333333333
#define ONEEPS 1.0000001
FORWARD(s_forward); /* spheroid */
xy.x = FXC * lp.lam * (xy.y = sqrt(4. - 3. * sin(fabs(lp.phi))));
xy.y = FYC * (2. - xy.y);
if ( lp.phi < 0.) xy.y = -xy.y;
return (xy);
}
INVERSE(s_inverse); /* spheroid */
lp.lam = xy.x / (FXC * ( lp.phi = 2. - fabs(xy.y) / FYC) );
lp.phi = (4. - lp.phi * lp.phi) * C13;
if (fabs(lp.phi) >= 1.) {
if (fabs(lp.phi) > ONEEPS) I_ERROR
else
lp.phi = lp.phi < 0. ? -HALFPI : HALFPI;
} else
lp.phi = asin(lp.phi);
if (xy.y < 0)
lp.phi = -lp.phi;
return (lp);
}
FREEUP; if (P) pj_dalloc(P); }
ENTRY0(eck2); P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P)
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