tmercator.c - plan9port - [fork] Plan 9 from user space
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       ---
       tmercator.c (567B)
       ---
            1 #include <u.h>
            2 #include <libc.h>
            3 #include "map.h"
            4 
            5 static int
            6 Xmercator(struct place *place, double *x, double *y)
            7 {
            8         if(fabs(place->nlat.l) > 80.*RAD)
            9                 return(-1);
           10         *x = -place->wlon.l;
           11         *y = 0.5*log((1+place->nlat.s)/(1-place->nlat.s));
           12         return(1);
           13 }
           14 
           15 proj
           16 mercator(void)
           17 {
           18         return(Xmercator);
           19 }
           20 
           21 static double ecc = ECC;
           22 
           23 static int
           24 Xspmercator(struct place *place, double *x, double *y)
           25 {
           26         if(Xmercator(place,x,y) < 0)
           27                 return(-1);
           28         *y += 0.5*ecc*log((1-ecc*place->nlat.s)/(1+ecc*place->nlat.s));
           29         return(1);
           30 }
           31 
           32 proj
           33 sp_mercator(void)
           34 {
           35         return(Xspmercator);
           36 }