Add latlon.c

helpers/latlon.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#define R 6371
+#define TO_RAD (3.1415926536 / 180)
+double dist(double th1, double ph1, double th2, double ph2)
+{
+	double dx, dy, dz;
+	ph1 -= ph2;
+	ph1 *= TO_RAD, th1 *= TO_RAD, th2 *= TO_RAD;
+
+	dz = sin(th1) - sin(th2);
+	dx = cos(ph1) * cos(th1) - cos(th2);
+	dy = sin(ph1) * cos(th1);
+	return asin(sqrt(dx * dx + dy * dy + dz * dz) / 2) * 2 * R;
+}
+
+int main(int argc, const char * argv[])
+{
+	if(argc < 5 || argc > 5){
+		return 1;
+	}
+	float coords[4];
+	for(int i=1;i<5;i++){
+		if(atof(argv[i]) == 0){
+			return 1;
+		}
+		coords[i] = atof(argv[i]);
+	}
+	
+	double d = dist(coords[1], coords[2], coords[3], coords[4]);
+	printf("%.1f\n", d);
+
+	return 0;
+}