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Jun 3, 2024 · Conversion between NAVD 88 (North American Vertical Datum of 1988) and NGVD 29 (National Geodetic Vertical Datum of 1929) varies spatially but can generally be approximated using the following conversion: NGVD 29 = NAVD 88 – 3.6 feet. This conversion is accurate within approximately ±0.5 feet for 95 percent of the study area.
Nov 4, 2020 · In a few years the key datum of the last 30 years, the North American Vertical Datum of 1988 — the datum used by federal agencies such as the Federal Emergency Management Agency and the U.S. Army Corps of Engineers — will be replaced by a new, satellite-based system. David B. Zilkoski, the former director of the National Geodetic Survey at ...
More broadly, a vertical datum is the entire system of the zero elevation surface and methods of determining heights relative to that surface. Over the years, many different types of vertical datums have been used. The most predominant types today are tidal datums and geodetic datums. Tidal datums are determined by averaging the level of water ...
The North American Vertical Datum of 1988 (NAVD 88) is the official vertical datum of the United States, having superseded the older National Geodetic Vertical Datum of 1929 (NGVD 29). Both NAVD 88 and NGVD 29 are geodetic datums, a reference surface of zero elevation to which heights are referred to over a large geographic extent.
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.
However when Sea Level Datum of 1929 (MSL) and was superseded by the NGVD 29 the numbers didn't change; it was a name change only. So, the 29 ft lake elevation the CoE referenced . is . NGVD 29. To convert to NGVD 29 to NAVD 88 you simply add 3.6 feet. So the 29 ft lake elevation (MSL or NGVD 29) is 32.6 ft NAVD 88. For a good writeup on this, see:
The vertical datum is a collection of specific points on the Earth with known heights either above or below mean sea level. Near coastal areas, mean sea level is determined with a tide gauge. In areas far away from the shore, mean sea level is determined by the shape of the geoid. Similar to the survey markers used to identify known positions ...
