Designation of Zone Boundaries. The zone boundary lines are intended generally to follow the center lines of streets; the center lines of railroad rights-of-way; existing lot lines; the center lines of rivers, streams and other waterways; and Municipal boundary lines. When a district boundary line does not follow such a line, its position shall be shown on the Zoning Map by a specific dimension expressing its distance, in feet, from a street line or other boundary line as indicated.