TOPOGRAPHIC SURVEYS - A topographic survey is a three dimensional survey in which features are not only located horizontally but are located vertically. The vertical changes on this type of survey are represented by contour lines on the map. Contour lines are lines of constant elevation. This type of survey is generally required when a site will be changed both horizontally and vertically, such as the development of raw land or re-development of an existing parcel. Often it is helpful if a boundary survey is included with a topographic survey but it is not essential.