计算地球上两点的距离

/**
 * 计算地球上两个点的距离
 * @author xuri002
 *
 */
public class DistCnvter {
	
	public enum GaussSphere {
		Beijing54, Xian80, WGS84,
	}

	private static double Rad(double d) {
		return d * Math.PI / 180.0;
	}

	public static double getDistance(double lng1, double lat1, double lng2,
			double lat2, GaussSphere gs) {
		double radLat1 = Rad(lat1);
		double radLat2 = Rad(lat2);
		double a = radLat1 - radLat2;
		double b = Rad(lng1) - Rad(lng2);
		double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2)
				+ Math.cos(radLat1) * Math.cos(radLat2)
				* Math.pow(Math.sin(b / 2), 2)));
		s = s* (gs == GaussSphere.WGS84 ? 6378137.0 : (gs == GaussSphere.Xian80 ? 6378140.0 : 6378245.0));
		s = Math.round(s * 10000) / 10000;
		return s;
	}
}