static double geoDistance_km(double lat1, double long1, double lat2, double long2) {
  double _eQuatorialEarthRadius = 6371;
  double _d2r = (Math.PI / 180D);
  double dlong = (long2 - long1) * _d2r;
  double dlat = (lat2 - lat1) * _d2r;
  double a = Math.pow(Math.sin(dlat / 2D), 2D) + Math.cos(lat1 * _d2r) * Math.cos(lat2 * _d2r)
          * Math.pow(Math.sin(dlong / 2D), 2D);
  double c = 2D * Math.atan2(Math.sqrt(a), Math.sqrt(1D - a));
  double d = _eQuatorialEarthRadius * c;
  return d;
}

Began life as a copy of #1008302