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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.
In common usage, elevations are often cited in height above sea level, although what "sea level" actually means is a more complex issue than might at first be thought: the height of the sea surface at any one place and time is a result of numerous effects, including waves, wind and currents, atmospheric pressure, tides, topography, and differences in the strength of gravity due to the presence ...
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
A common and relatively straightforward mean sea-level standard is instead a long-term average of tide gauge readings at a particular reference location. [1] The term above sea level generally refers to the height above mean sea level (AMSL). The term APSL means above present sea level, comparing sea levels in the past with the level today.
In North America elevations are given using either Sea Level Datum of 1929, also called the National Geodetic Vertical Datum of 1929 (NGVD 29) or the North American Vertical Datum of 1988 (NAVD 88).
Sea Level Datum 1929: OSGB36: Ordnance Survey Great Britain 1936: SK-42: Systema Koordinat 1942 goda: ED50: European Datum 1950: SAD69: South American Datum 1969: GRS 80: Geodetic Reference System 1980: ISO 6709: Geographic point coord. 1983: NAD 83: North American Datum 1983: WGS 84: World Geodetic System 1984: NAVD 88: N. American Vertical ...
The U.S. will no longer allow the import of seafood linked to the bycatch of marine mammals. Each year, over 650,000 marine mammals, including seals, whales, and dolphins, are killed by ...
Since the Sea Level Datum of 1929 was a hybrid model, it was not a pure model of mean sea level, the geoid, or any other equipotential surface. Therefore, it was renamed the National Geodetic Vertical Datum of 1929 (NGVD 29) May 10, 1973, by the National Geodetic Survey , a part of the National Oceanic and Atmospheric Administration .