The purpose of this ordinance is that of dividing the city into zones or districts restricting and regulating therein the location, erection, construction, reconstruction, alteration and use of buildings, structures and land of trade, industry, residences and other specified uses; to regulate the intensity of the use of lot areas, and to regulate and determine the area of open spaces surrounding such buildings; to establish building lines and the location of buildings designed for specified industrial, business, residential and other uses within such areas; to fix standards to which buildings or structures shall conform therein; to prohibit uses, buildings or structures incompatible with the character of such districts, respectively; to prevent additions to and alterations or remodeling of existing buildings or structures in such a way as to avoid the restrictions and limitations lawfully imposed hereunder; to limit congestion in the public streets by providing for the off-street parking and loading and unloading of vehicles; providing for the gradual elimination of nonconforming uses of land, building and structures; and prescribing penalties for the violation of the ordinance; to lessen congestion in the streets; to secure safety from fire, panic and other dangers; to provide adequate light and air; to prevent the overcrowding of land; to conserve the taxable value of land and buildings throughout the city; and to promote the public health, safety and general welfare.