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- Using this latitude and longitude, the conversion factor is 2.986 and the building elevation in NAVD 88 is 57.186.
www.broward.org › Environment › FloodZoneMapsConverting Existing Elevations When the Flood Map Vertical ...
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How do I convert NGVD 29 elevation to NAVD 88?
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Elevations referenced to NGVD 29 can be converted to NAVD 88 by using a conversion factor. This conversion factor is just added to the NGVD 29 elevation to compute the equivalent NAVD 88 elevation. The simplest method is to use the offset used by FEMA. In the eastern United States, the conversion factor is generally a single value for the
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After that time, NAVD 88 became the vertical datum of choice for FIS/FIRM production. Because existing flooding hazard data referenced to NGVD 29 may not be revised in the scope of an ongoing FIS/FIRM restudy, there is a need to enable efficient conversion of unrevised flood elevations to NAVD 88. It is FEMA’s goal to convert all flood maps ...
Jul 12, 2018 · The North American Vertical Datum of 1988 (NAVD 88) is the vertical control datum established in 1991 by the minimum-constraint adjustment of the Canadian-Mexican-United States leveling observations.
Conversion between NAVD 88 and the commonly used NGVD 29 varies spatially; however, over most of the study area the following conversion can be used: NGVD 29 = NAVD 88 –3.6 feet. This conversion generally is accurate within about ± 0.5 feet for 95 percent of the study area.
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. The difference of -0.88 is referred to as the “shift” between datums.
The equivalent NAVD 88 elevation can be obtained using the FEMA-approved average conversion factor in the following formula: NAVD 88 = NGVD 29 + conversion factor NAVD 88 = 10.0’ NGVD + (-1.51)
Preliminary analyses indicate differences for the conterminous United States between orthometric heights referred to NAVD 88 and to the National Geodetic Vertical Datum of 1929 (NGVD 29) range from -40 cm to +150 cm. In Alaska, the differences range from +94 cm to +240 cm.
