xref: /plan9/sys/src/cmd/map/libmap/trapezoidal.c (revision 59cc4ca53493a3c6d2349fe2b7f7c40f7dce7294)
1*59cc4ca5SDavid du Colombier #include <u.h>
2*59cc4ca5SDavid du Colombier #include <libc.h>
33e12c5d1SDavid du Colombier #include "map.h"
43e12c5d1SDavid du Colombier 
53e12c5d1SDavid du Colombier static struct coord stdpar0, stdpar1;
6219b2ee8SDavid du Colombier static double k;
7219b2ee8SDavid du Colombier static double yeq;
83e12c5d1SDavid du Colombier 
93e12c5d1SDavid du Colombier static int
Xtrapezoidal(struct place * place,double * x,double * y)10219b2ee8SDavid du Colombier Xtrapezoidal(struct place *place, double *x, double *y)
113e12c5d1SDavid du Colombier {
123e12c5d1SDavid du Colombier 	*y = yeq + place->nlat.l;
133e12c5d1SDavid du Colombier 	*x = *y*k*place->wlon.l;
143e12c5d1SDavid du Colombier 	return 1;
153e12c5d1SDavid du Colombier }
163e12c5d1SDavid du Colombier 
173e12c5d1SDavid du Colombier proj
trapezoidal(double par0,double par1)18219b2ee8SDavid du Colombier trapezoidal(double par0, double par1)
193e12c5d1SDavid du Colombier {
203e12c5d1SDavid du Colombier 	if(fabs(fabs(par0)-fabs(par1))<.1)
213e12c5d1SDavid du Colombier 		return rectangular(par0);
223e12c5d1SDavid du Colombier 	deg2rad(par0,&stdpar0);
233e12c5d1SDavid du Colombier 	deg2rad(par1,&stdpar1);
243e12c5d1SDavid du Colombier 	if(fabs(par1-par0) < .1)
253e12c5d1SDavid du Colombier 		k = stdpar1.s;
263e12c5d1SDavid du Colombier 	else
273e12c5d1SDavid du Colombier 		k = (stdpar1.c-stdpar0.c)/(stdpar0.l-stdpar1.l);
283e12c5d1SDavid du Colombier 	yeq = -stdpar1.l - stdpar1.c/k;
293e12c5d1SDavid du Colombier 	return Xtrapezoidal;
303e12c5d1SDavid du Colombier }
31