比较两个经纬度之间的直线距离

    public static double distanceByLongNLat(double long1, double lat1, double long2, double lat2) {
        double a, b, R;
        R = 6378137;//地球半径
        lat1 = lat1 * Math.PI / 180.0;
        lat2 = lat2 * Math.PI / 180.0;
        a = lat1 - lat2;
        b = (long1 - long2) * Math.PI / 180.0;
        double d;
        double sa2, sb2;
        sa2 = Math.sin(a / 2.0);
        sb2 = Math.sin(b / 2.0);
        d = 2 * R * Math.asin(Math.sqrt(sa2 * sa2 + Math.cos(lat1) * Math.cos(lat2) * sb2 * sb2));
        return d;
    }