include <math.h>

ifdef WIN32

define round(x) floor(x+0.5)

endif /WIN32/

define PI 3.1415926535897

static const double EARTH_RADIUS = 6378.137;





//////////////////////////////////////////////////////////////////////////





double rad(double d)

{

return d PI / 180.0;

}





double GetDistance(double lat1, double lng1, double lat2, double lng2)

{

double radLat1 = (double)rad(lat1);

double radLat2 = rad(lat2);

double a = radLat1 - radLat2;

double b = rad(lng1) - rad(lng2);

double s = 2 asin(sqrt(pow(sin(a/2),2) +

cos(radLat1)cos(radLat2)pow(sin(b/2),2)));

//

s = s EARTH_RADIUS;

s = round(s 10000) / 10000;

return s;

}