Where uncertainty exists with respect to the boundaries of various zones, the following rules shall apply: A. Where the intended boundaries on the zone map are approximately street or alley lines, said streets or alleys shall be construed to be the zone boundaries; B. Where the indicated boundaries are approximately lot lines, said lot lines shall be construed to be the zone boundaries, unless otherwise indicated; C. Where land has not been subdivided into lots, the zone boundary shall be determined by the use of the scale of measurement shown on the map;