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Nov 4, 2020 · In the late 19th century and through the early decades of the 20th, multiple vertical datums — the standard for accurate measurement of elevation across large distances — existed across the country.
The North American Vertical Datum of 1988 ( NAVD 88) is the vertical datum for orthometric heights established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.
NAVD 88 is the abbreviation for the North American Vertical Datum of 1988. NAVD 88 is one of five current National Geodetic Datums, which are coordinate systems that act as standard reference lines to measure points on the earth’s surface in the region that they apply. A datum cannot be seen or physically measured because is a calculation of the Geoid/Mean Seal Level (MSL), which is the ...
The Benchmark indicates that at zero feet in NAVD88 is equal to 2.75 feet MLLW. So to convert a MLLW height in our area to a NAVD88 height just subtract 2.75 feet or conversely to change a NAVD88 height to MLLW height you add 2.75 feet.
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The new adjustment, NAVD 88, was completed in June 1991. It is now the only official vertical datum in the United States. NAVD 88 was created by adding 625,000 kilometers of leveling, performed after NGVD 29 was established, and by performing a major least squares adjustment that constrained only a single tide station at zero elevation.
The Sea Level Datum of 1929 was established by averaging the mean sea level elevation at 26 tidal stations located in the United States and Canada. As can be surmised from this statement, mean sea level varies at different locations.
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What does NAVD 88 mean?
Is NGVD 29 the same as NAVD 88?
Which vertical datum standards are supported by FEMA?
How high is NAVD88 in MLLW?
Within the boundaries of the District, the NAVD 88 elevation number is a shift of approximately 0.7 to 1.1 feet lower that the elevation in the NGVD 29 standard. This variation is due to geographical differences. For example, a water level for Lake Panasoffkee of 39.24 feet in NGVD 29 will be 38.36 in the NAVD 88 standard.
