//计算两点位置距离

  getDistance: function (lat1, lng1, lat2, lng2) {

    lat1 = lat1 || 0;

    lng1 = lng1 || 0;

    lat2 = lat2 || 0;

    lng2 = lng2 || 0;

    var rad1 = lat1 * Math.PI / 180.0;

    var rad2 = lat2 * Math.PI / 180.0;

    var a = rad1 - rad2;

    var b = lng1 * Math.PI / 180.0 - lng2 * Math.PI / 180.0;

    var r = 6378137;

    var distance = r * 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2) + Math.cos(rad1) * Math.cos(rad2) * Math.pow(Math.sin(b / 2), 2)));

    /*if (distance > 1000){

      distance = Math.round(distance / 1000);

    }*/

    return distance;

  }