code: public static double getLongitudeDistance(BoundingBox boundingBox) {
          return getLongitudeDistance(boundingBox.getMinLongitude(),
                  boundingBox.getMaxLongitude(),
                  (boundingBox.getMinLatitude() + boundingBox.getMaxLatitude()) / 2.0);
      }
docs: Get the longitude distance in the middle latitude
  
  @param boundingBox bounding box
  @return distance