Where the boundary lines on the Zoning Map or the Water Resource Districts Map are within the street lines of public or private ways, the center lines of such ways shall be the boundary lines.

Where the boundary lines are shown approximately on the location of property or lot lines and the exact location of property, lot or boundary lines is not indicated by means of dimensions shown in figures, then the property or lot lines shall be the boundary lines.

Where the boundary lines are located outside of such street lines and shown approximately parallel thereto, they shall be regarded as parallel to such street lines, and dimensions shown in figures placed upon said map between such boundary lines and street side lines are the distances in feet of such boundary lines from such street side lines, such distances being measured at right angles to such street lines unless otherwise indicated.

Where the location of boundary lines is uncertain, it shall be determined by the distance in feet, if given, from other lines upon said map, by the use of identifications as shown on the map or by the scale of the map.

Where a district boundary line between a residential, business and/or industrial district divides any lot existing at the time such line is adopted, the regulations for the less-restricted portions of such lot shall extend no more than 30 feet into the more-restricted portion, provided that the lot has frontage in the less-restricted district.

Where boundary lines are contour lines, they are at an indicated elevation above the datum which is mean sea level of the United States Geological Survey.