Every local planning authority shall, within such time as may be prescribed prepare a present land and building use map hereinafter called “the map indicating the present use of lands and buildings in the planning area:
Provided that if any local authority has been declared as the local planning authority of any area under sub-section (1) of section 11 and such local authority has prepared a map of the area before the date of commencement of this Act in that area, then, the map already prepared by such local authority shall be deemed to be a map prepared under this section.
Explanation.- For the purpose of this section, the present land and building use shall be the predominant use to which the land or the building, as the case may be, is put to in the date of preparation of the map by the local planning authority.