Every sign erected or proposed to be erected within leased areas of the Provo Municipal Airport shall be classified by the City zoning administrator in accordance with the definitions of signs contained in Section 14.38.160, Provo City Code. Any sign which does not clearly fall within one (1) of the classifications, shall be placed in the classifications which the sign, in view of its design, location, and purpose, most clearly approximates in the opinion of said zoning administrator.