经纬度计算距离

感谢zhijun.wu

 public static double distanceByLngLat(double lat1,double lng1, double lat2,double lng2) {
	        double radLat1 = lat1 * Math.PI / 180;
	        double radLat2 = lat2 * Math.PI / 180;
	        double a = radLat1 - radLat2;
	        double b = lng1 * Math.PI / 180 - lng2 * Math.PI / 180;
	        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 * 6378137.0;// 取WGS84标准参考椭球中的地球长半径(单位:m)
	        s = Math.round(s * 10000) / 10000;

	        return s;
	    }
	public static void main(String[] args) throws Exception {
	    System.out.println(distanceByLngLat(31.20985, 121.4171,31.21051, 121.4431));
	}