A Topographic Survey is a Survey that gathers field data of the ground elevations on and around a property and presents this data as contour lines on a plan which provides a horizontal depiction of the vertical nature of the terrain and usually needs to be based on a known vertical datum such as North American Vertical Datum of 1988 (NAVD88), National Geodetic Vertical Datum of of 1929 (NGVD29), Boston City Base Datum, etc.