polyconic.c (584B)
1 #include <u.h> 2 #include <libc.h> 3 #include "map.h" 4 5 int 6 Xpolyconic(struct place *place, double *x, double *y) 7 { 8 double r, alpha; 9 double lat2, lon2; 10 if(fabs(place->nlat.l) > .01) { 11 r = place->nlat.c / place->nlat.s; 12 alpha = place->wlon.l * place->nlat.s; 13 *y = place->nlat.l + r*(1 - cos(alpha)); 14 *x = - r*sin(alpha); 15 } else { 16 lon2 = place->wlon.l * place->wlon.l; 17 lat2 = place->nlat.l * place->nlat.l; 18 *y = place->nlat.l * (1+(lon2/2)*(1-(8+lon2)*lat2/12)); 19 *x = - place->wlon.l * (1-lat2*(3+lon2)/6); 20 } 21 return(1); 22 } 23 24 proj 25 polyconic(void) 26 { 27 return(Xpolyconic); 28 }