The building depth refers to the second dimension of the building ground plan (which will be displayed vertically on the screen). It must be in units compatible with the department areas. The building area is computed as the product of the building width and depth. The building area is computed as the product of the building width and building depth. The building and department areas should be expressed in compatible units to the building width and depth, i.e., if the building depth and width are expressed in feet then the building and department areas must be expressed in square feet.