xref: /plan9-contrib/sys/src/cmd/map/libmap/simpleconic.c (revision 219b2ee8daee37f4aad58d63f21287faa8e4ffdc)
1 #include "map.h"
2 
3 static double r0, a;
4 
5 static int
6 Xsimpleconic(struct place *place, double *x, double *y)
7 {
8 	double r = r0 - place->nlat.l;
9 	double t = a*place->wlon.l;
10 	*x = -r*sin(t);
11 	*y = -r*cos(t);
12 	return 1;
13 }
14 
15 proj
16 simpleconic(double par0, double par1)
17 {
18 	struct coord lat0;
19 	struct coord lat1;
20 	deg2rad(par0,&lat0);
21 	deg2rad(par1,&lat1);
22 	if(fabs(lat0.l+lat1.l)<.01)
23 		return rectangular(par0);
24 	if(fabs(lat0.l-lat1.l)<.01) {
25 		a = lat0.s/lat0.l;
26 		r0 = lat0.c/lat0.s + lat0.l;
27 	} else {
28 		a = (lat1.c-lat0.c)/(lat0.l-lat1.l);
29 		r0 = ((lat0.c+lat1.c)/a + lat1.l + lat0.l)/2;
30 	}
31 	return Xsimpleconic;
32 }
33