JAVA計算兩個經緯度距離的N種方式

Solr裏用到的 geohash

public static final double DEGREES_TO_RADIANS = Math.PI / 180.0;
    public static final double RADIANS_TO_DEGREES = 180.0 / Math.PI;
    //地球半徑
    public static final double EARTH_MEAN_RADIUS_KM = 6371.009;
    //地球直徑
    private static final double EARTH_MEAN_DIAMETER = EARTH_MEAN_RADIUS_KM * 2;

    /***
     * 距離半徑計算方式
     * @param latCenterRad  中心點經緯度
     * @param lonCenterRad
     * @param latVals  目標經緯度
     * @param lonVals
     * @return 兩座標的距離 單位千米
     */
    public static double getDistance(double latCenterRad, double lonCenterRad, double latVals, double lonVals) {
        //計算經緯度
        double latRad = latVals * DEGREES_TO_RADIANS;
        double lonRad = lonVals * DEGREES_TO_RADIANS;

        //計算經緯度的差
        double diffX = latCenterRad * DEGREES_TO_RADIANS - latRad;
        double diffY = lonCenterRad * DEGREES_TO_RADIANS - lonRad;
        //計算正弦和餘弦
        double hsinX = Math.sin(diffX * 0.5);
        double hsinY = Math.sin(diffY * 0.5);
        double latCenterRad_cos = Math.cos(latCenterRad * DEGREES_TO_RADIANS);
        double h = hsinX * hsinX + (latCenterRad_cos * Math.cos(latRad) * hsinY * hsinY);

        return (EARTH_MEAN_DIAMETER * Math.atan2(Math.sqrt(h), Math.sqrt(1 - h)));
    }