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A vertical datum is a surface of zero elevation to which heights of various points are referenced. Traditionally, vertical datums have used classical survey methods to measure height differences (i.e. geodetic leveling) to best fit the surface of the earth. The current vertical datum for the contiguous United States and Alaska is the North ...
The World Geodetic System ( WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS. The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also describes the associated Earth Gravitational Model (EGM) and World Magnetic Model (WMM).
The "ellipsoid" used in horizontal datums is close approximation of Earth's surface. While you can use a horizontal datum to determine height simply because it is a 3D model, it is not as useful as a geoid (used in vertical datums) which has some "physical" meaning because it approximates mean sea level fairly accurately.
A geodetic datum is an abstract coordinate system with a reference surface (such as an ellipsoid) that serves to provide known locations to begin surveys and create maps. There are two main types of datums. Horizontal datums provide a reference for positions (latitude and longitude) on the surface of the Earth, while vertical datums are
A horizontal datum, which binds the abstract coordinate system to the real space of the Earth. A horizontal datum can be defined as a precise reference framework for measuring geographic coordinates (latitude and longitude). Examples include the World Geodetic System and the 1927 and 1983 North American Datum.
1 Many different definitions of a horizontal datum (also known as geodetic datum) exist. However, a practical working definition in use is: “A horizontal datum is a reference system for specifying positions on the Earth’s surface. Each datum is associated with a particular reference spheroid that can be different in size, orientation and
This system is known as a horizontal datum. Historically, horizontal datums have been defined by the ellipsoid parameters being used for the mathematical equations and the latitude and longitude of a single point on that ellipsoid with an azimuth to another close-by point for orientation. This latitude, longitude and orientation are determined ...
