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WebSVN – planix.SVN – Blame – /os/branches/feature_tlsv12/sys/src/cmd/map/libmap/elliptic.c – Rev 2

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#include <u.h>
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#include <libc.h>
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#include "map.h"
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struct coord center;
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static int
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Xelliptic(struct place *place, double *x, double *y)
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{
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	double r1,r2;
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	r1 = acos(place->nlat.c*(place->wlon.c*center.c
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		- place->wlon.s*center.s));
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	r2 = acos(place->nlat.c*(place->wlon.c*center.c
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		+ place->wlon.s*center.s));
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	*x = -(r1*r1 - r2*r2)/(4*center.l);
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	*y = (r1*r1+r2*r2)/2 - (center.l*center.l+*x**x);
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	if(*y < 0)
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		*y = 0;
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	*y = sqrt(*y);
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	if(place->nlat.l<0)
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		*y = -*y;
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	return(1);
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}
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proj
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elliptic(double l)
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{
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	l = fabs(l);
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	if(l>89)
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		return(0);
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	if(l<1)
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		return(Xazequidistant);
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	deg2rad(l,&center);
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	return(Xelliptic);
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}