What is a vertical datum in geodesy and cartography?

A vertical datum is a reference coordinate surface used to determine vertical positions such as terrain elevations, water levels, and built structures. Common criteria for establishing these datums include tidal observations, gravimetric models based on a geoid, or geometric Earth ellipsoids. They provide an essential standard for mapping, navigation, and surveying across the globe.

What we know

• A vertical datum serves as a reference coordinate surface used to measure vertical positions like terrain elevation, bathymetry, water levels, and satellite orbit altitudes. [1, 2]
• Commonly adopted criteria for establishing a vertical datum include tidal observations, gravimetric geoids, and geometric Earth ellipsoids. [2]
• The North American Vertical Datum of 1988 (NAVD 88) superseded the National Geodetic Vertical Datum of 1929 for vertical control surveying in the United States. [3, 4]
• The Australian Height Datum was introduced in 1971 as an amalgamation of spirit leveling work corrected to align with mean sea level observations from thirty coastal tide gauges. [5]

Still open

• Newer technologies have uncovered numerous deficiencies, offsets, and distortions within the Australian Height Datum, though it remains the published datum for engineering operations.

Where to go next

• how it workedHow do tidal observations help establish vertical datums?
• a case in pointWhat is the North American Vertical Datum of 1988?
• compared withHow does a horizontal datum differ from a vertical datum?
• the bigger pictureWhat role does gravity play in modern geodetic systems?
• whenWhen was the Australian Height Datum established?
• an unexpected connectionWhy do planetary scientists need vertical datums?Vertical datums are not restricted to Earth mapping; they are also applied in planetary science as zero-elevation surfaces to measure features across other worlds.

Sources

• [1]vertical datum (Wikidata Q9364781) · CC0 1.0
• [2]Vertical datum · CC BY-SA 4.0
• [3]North American Vertical Datum of 1988 · CC BY-SA 4.0
• [4]National Geodetic Vertical Datum of 1929 · CC BY-SA 4.0
• [5]Australian Height Datum · CC BY-SA 4.0