Unless otherwise expressly stated, when the provisions of this Zoning Code require that two or more uses be separated by some minimum distance, the separation distance shall be measured from lot line to lot line along the shortest imaginary line between the subject lots. Where uses are required to be separated by some minimum distance from a zoning district boundary, the separation distance shall be measured from the lot line to the zoning district boundary along the shortest imaginary line between the lot and the zoning boundary.