地图经纬度距离计算

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

/***
   * 距离半径计算方式
   * @param latCenterRad  中心点经纬度
   * @param lonCenterRad
   * @param latVals  目标经纬度
   * @param lonVals
   * @return 两坐标的距离 单位千米
   */
  public static double doubleVal(double latCenterRad, double lonCenterRad, double latVals, double lonVals) {
    //计算经纬度
    double latRad = latVals * DEGREES_TO_RADIANS;
    double lonRad = lonVals * DEGREES_TO_RADIANS;

    //计算经纬度的差
    double diffX = latCenterRad * DEGREES_TO_RADIANS - latRad;
    double diffY = lonCenterRad * DEGREES_TO_RADIANS - lonRad;
    //计算正弦和余弦
    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)));
  }