计算两个坐标之间的距离

public class DistanceInMeter
{
	
public static double distFrom(double lat1, double lng1, double lat2, double lng2) {
    double earthRadius = 3958.75;
    double dLat = toRadians(lat2-lat1);
    double dLng = toRadians(lng2-lng1);
    double a = Math.Sin(dLat/2) * Math.Sin(dLat/2) +
               Math.Cos(Math.toRadians(lat1)) * Math.Cos(Math.toRadians(lat2)) *
               Math.Sin(dLng/2) * Math.Sin(dLng/2);
    double c = 2 * Math.Atan2(Math.sqrt(a), Math.sqrt(1-a));
    double dist = earthRadius * c;

    int meterConversion = 1609;

    return (dist * meterConversion);
    }

	static double  toRadians(double degree)
	{
		return (degree*0.0174532925 );
	}
}