add more comments in README.md

1 files changed, 11 insertions, 3 deletions

diff --git a/gridcal.c b/gridcal.c
index 97e8cf9..6e552b4 100644
--- a/gridcal.c
+++ b/gridcal.c
@@ -15,8 +15,16 @@
 #include <ctype.h>
 
 #define MIN(a,b) ((a)>(b)?(b):(a))
+#define R 6371
 
-double R = 6371;
+#ifndef M_PI
+#define M_PI           3.14159265358979323846  /* pi */
+#endif
+
+
+#ifndef M_PI_2
+#define M_PI_2         1.57079632679489661923  /* pi/2 */
+#endif
 
 typedef struct {
 	double lat;
@@ -26,7 +34,7 @@ typedef struct {
 
 void usage(char *argv0){
 
-	printf("Usage: %s <grid1> <grid2> [<pwr>]", argv0);
+	printf("Usage: %s <loc1> [<loc2> [<pwr>]]", argv0);
 	exit(1);
 }
 
@@ -117,7 +125,7 @@ int main(int argc, char *argv[]){
 		loc1[n1] = '\0';
 		check_input(loc1);
 		grid_to_latlon(loc1, &c1);
-		printf("%s %g %g\n", loc1, c1.lat, c1.lon);
+		printf("%s %g %g %g %g\n", loc1, c1.lat*180/M_PI, c1.lon*180/M_PI, c1.lat, c1.lon);
 		exit(0);
 	}