The district boundaries are either streets or alleys, unless otherwise shown, and where the designation on the district map indicates that the various districts are approximately bounded by a street or alley line, said street or alley line shall be construed to be the district boundary line.

Where the district boundaries are not otherwise indicated and where the property has been or may hereafter be divided into blocks and lots, the district boundaries shall be construed to be lot lines, and where the designations on the district map are approximately bounded by lot lines, said lot lines shall be construed to be the boundary of the district.

In unsubdivided property, the district boundary lines shown on the district map shall be determined by use of the scale shown on such map.