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NAVD 88 was established in 1991 by the minimum-constraint adjustment of geodetic leveling observations in Canada, the United States, and Mexico. It held fixed the height of the primary tide gauge benchmark , referenced to the International Great Lakes Datum of 1985 local mean sea level (MSL) height value, at Rimouski , Quebec , Canada .
Vertical measurements, based on distances above or below Mean High Water (MHW), are calculated using the North American Vertical Datum of 1988 (NAVD 88). [ 1 ] NAD 83, along with NAVD 88, is set to be replaced with a new GPS - and gravimetric geoid model-based geometric reference frame and geopotential datum, potentially in 2025 .
The system is based on the datums NAD 83 and NAVD 88. [3] In 2024 or 2025, [needs update] the NSRS will be modernized with a focus on Global Navigation Satellite Systems (GNSS) and geoid use. It will use the following four frames of reference, each representing a tectonic plate: [4] [5] North American Terrestrial Reference Frame of 2022 (NATRF2022)
An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations. It is a spheroid (an ellipsoid of revolution) whose minor axis (shorter diameter), which connects the ...
v. t. e. A spatial reference system (SRS) or coordinate reference system (CRS) is a framework used to precisely measure locations on the surface of Earth as coordinates. It is thus the application of the abstract mathematics of coordinate systems and analytic geometry to geographic space. A particular SRS specification (for example, " Universal ...
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 1980 Geodetic Reference System (GRS 80) posited a 6 378 137 m semi-major axis and a 298.257222101 flattening. This system was adopted at the XVII General Assembly of the International Union of Geodesy and Geophysics (IUGG) in Canberra, Australia, 1979. The GRS 80 reference system was originally used by the World Geodetic System 1984 (WGS 84).
t. e. EPSG Geodetic Parameter Dataset (also EPSG registry) is a public registry of geodetic datums, spatial reference systems, Earth ellipsoids, coordinate transformations and related units of measurement, originated by a member of the European Petroleum Survey Group (EPSG) in 1985. Each entity is assigned an EPSG code between 1024 and 32767 ...