code: public final double getDistanceToKm(Position position) {
  		double lat1 = toRadians(lat);
  		double lat2 = toRadians(position.lat);
  		double lon1 = toRadians(lon);
  		double lon2 = toRadians(position.lon);
  		double deltaLon = lon2 - lon1;
  		double cosLat2 = cos(lat2);
  		double cosLat1 = cos(lat1);
  		double sinLat1 = sin(lat1);
  		double sinLat2 = sin(lat2);
  		double cosDeltaLon = cos(deltaLon);
  		double top = sqrt(sqr(cosLat2 * sin(deltaLon))
  				+ sqr(cosLat1 * sinLat2 - sinLat1 * cosLat2 * cosDeltaLon));
  		double bottom = sinLat1 * sinLat2 + cosLat1 * cosLat2 * cosDeltaLon;
  		double distance = radiusEarthKm * atan2(top, bottom);
  		return abs(distance);
  	}
docs: returns distance between two WGS84 positions according to Vincenty's
  formula from Wikipedia
  
  @param position
  @return