ref: b9745c60a1bf2a3876e411d38c67a0980d70e3a3
dir: /sys/src/cmd/map/libmap/mercator.c/
#include <u.h> #include <libc.h> #include "map.h" static int Xmercator(struct place *place, double *x, double *y) { if(fabs(place->nlat.l) > 80.*RAD) return(-1); *x = -place->wlon.l; *y = 0.5*log((1+place->nlat.s)/(1-place->nlat.s)); return(1); } proj mercator(void) { return(Xmercator); } static double ecc = ECC; static int Xspmercator(struct place *place, double *x, double *y) { if(Xmercator(place,x,y) < 0) return(-1); *y += 0.5*ecc*log((1-ecc*place->nlat.s)/(1+ecc*place->nlat.s)); return(1); } proj sp_mercator(void) { return(Xspmercator); }