This chapter classifies and regulates the use of land, buildings and structures within the corporate limits of the city, as hereinafter set forth. The regulations contained herein are necessary to promote the health, safety, convenience and welfare of the inhabitants by dividing the city into zoning districts and regulating therein the use of the land and the use and size of buildings as to height and number of stories, the coverage of the land by buildings, the size of yards and open spaces, the location of buildings and the density of population.