package com.elephant.framework.galaxy.aroad.util;

/**
 * @program:
 * @description: 位置距离帮助类
 * @author: songwenjie
 * @create: 2019-04-02 10:09
 **/
public class LocationUtil {

    private static double EARTH_RADIUS = 6378.137;

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

    /**
     * 通过经纬度计算距离(单位：千米)
     * @param lat1 起点纬度
     * @param lng1 起点经度
     * @param lat2 终点纬度
     * @param lng2 终点经度
     * @return
     */
    public static double calculateDistance(double lat1, double lng1,
                                           double lat2, double lng2) {
        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 * EARTH_RADIUS;
        s = Math.round(s * 10000d) / 10000d;
        return s;
    }
}
