The district boundaries are either streets or alleys, unless otherwise shown, and where the districts designated on the district map are bounded approximately by streets or alleys, such streets or alleys shall be construed to be the boundary of the district.
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 the lot lines. Where the districts designated on the map are bounded approximately by lot lines, the lot lines shall be construed to be the boundary of the district unless the boundaries are otherwise indicated on the map.
In unsubdivided property, the district boundary lines on the map shall be determined by use of the scale appearing on the map.
Where the district boundary is a railroad line, such boundary shall be construed to be the centerline of the main track. In the case of an abandoned railroad line, the centerline of the right-of-way shall be construed as the district boundary.