Land Survey Elevation Marker

The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that early surveyors made in stone structures, into which an angle-iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future. Naturally today's benchmarks are more modern. With modern technology allowing for very accurate horizontal and vertical position. The term is generally applied to any monument used to mark a point as an elevation reference. Frequently, these monuments are bronze, brass or aluminum disks and are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point.

The City of Phoenix uses the most technologically advanced survey equipment and software programs to enhance our horizontal and vertical datums. Currently our vertical system is based on National Geodetic Vertical Datum (NGVD) 29 Datum and our horizontal datum is based on North American Datum (NAD) 83 datum. All of this will change with the coming of the NGS 2022 Datum to be initiated in the future. This datum will be the basis for a new vertical and horizontal datum from NGS.

Datum Uses: Surveyors, Engineers, Architects, Flood Managers, GIS Professionals and others use this data to verify the vertical positional accuracy of geographic data and to provide the basis of elevations for all new engineering design plans. These markers are critical to surveying, mapping, GIS applications, subsidence studies, infrastructure improvements and engineering design projects, within the City of Phoenix. These marks are cared for and the data updated by the City of Phoenix, Streets Department, Design and Construction, Survey Team.