Changes in the boundaries of the zones shall be made by adopting an amended zoning map, or part of the map, which amended map or part so adopted shall become a part of this code.

No changes in the boundaries of any zone shall be approved unless such change is found to be in compliance with the comprehensive plan.

Boundaries shown as approximately following the centerlines of streets, alleys or highways shall be construed as following such centerlines.

Boundaries indicated as approximately following lot lines shall be construed as following such lot lines.

Distances not specifically indicated on the official zoning map shall be determined by applying the scale of the map.

Where a zone boundary line is parallel, or approximately parallel, to a street and divides a lot or property in single ownership having street frontage in a less restrictive zone, the provisions applicable to the less restrictive zone may be extended to the entire lot, but in no case for a distance of more than 25 feet. Where the zone boundary line divides a lot having street frontage only in a more restrictive zone, the provisions of this title covering the more restrictive portion of the lot shall extend to the entire lot.

Where a zone boundary line divides a lot of single ownership and the line is at right angles or approximately at right angles to the street, highway or place upon which the lot fronts, the provisions of this title applicable in the less restrictively zoned portion of the lot may be extended to the entire lot or for a distance of 25 feet from the zone boundary line, whichever is the lesser distance.