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1. • NGVD 29 = NAVD 88 –3.6 feet

     • 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.
     pubs.usgs.gov › sir › 2010

     Conversion Factors and Datums - USGS Publications Warehouse

2. People also ask

   What is a vertical datum conversion?

   • As stated in Standard 121, the vertical datum conversion shall be applied to flood elevations reported on the FIRM, Flood Profiles shown in the FIS Report, and all data tables in the FIS Report that document flood elevations.

   Guidance for Flood Risk Analysis and Mapping - FEMA.gov

   www.fema.gov/sites/default/files/2020-02/Vertical_Datum_Conversion_Guidance_May_2014.pdf

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   What is the current vertical datum for the United States & Alaska?

   • The current vertical datum for the contiguous United States and Alaska is the North American Vertical Datum of 1988. Hawaii, Puerto Rico and Pacific Island territories have separately defined datums. (See Table 1)

   National Geodetic Survey - Vertical Datums - National Oceanic and

   www.ngs.noaa.gov/datums/vertical/

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   Is the standard vertical datum conversion program (vertcon) applicable?

   • In these cases, the standard Vertical Datum Conversion Program (VERTCON) conversion software discussed here is not applicable, but the general principles for defining areas for applying a uniform conversion factor by testing a sampling of points and limiting maximum variation from the average conversion factor to 0.25ft can still be applied.

   Guidance for Flood Risk Analysis and Mapping - FEMA.gov

   www.fema.gov/sites/default/files/2020-02/Vertical_Datum_Conversion_Guidance_May_2014.pdf

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   When did the NGS adopt a vertical datum?

   • During the 1970s, the NGS, and counterpart agencies in Mexico and Canada, adopted a vertical datum based on a surface that would closely approximate the Earth’s geoid. The new adjustment, NAVD88, was completed in June 1991 and is now the only official vertical datum in the United States.

   Guidance for Flood Risk Analysis and Mapping - FEMA.gov

   www.fema.gov/sites/default/files/2020-02/Vertical_Datum_Conversion_Guidance_May_2014.pdf

   See all results for this question

3. www.vdatum.noaa.gov › vdatumwebOnline VDatum: Vertical Datums Transformation

   www.vdatum.noaa.gov › vdatumweb

   • Cached

   Web VDatum is designed to vertically transform geospatial data among a variety of tidal, orthometric and ellipsoidal vertical datums - allowing users to convert their data from different horizontal/vertical references into a common system and enabling the fusion of diverse geospatial data in desired reference levels.

   • Vertical Datums

     The current vertical datum for the contiguous United States...

   • Vertcon 3.0

     The actual transformation tool is NGS’s Coordinate...

   • Datum Tutorial

     Referenced Ellipsoid. GEOID. Horizontal Datum : NAD83 ,...

   • Vertical Datums Transformation

     VDatum is a free software tool being developed jointly by...

4. www.ngs.noaa.gov › NCATNGS Coordinate Conversion and Transformation Tool (NCAT)

   www.ngs.noaa.gov › NCAT

   • Cached

   May 21, 2024 · For coordinate conversion, NCAT allows conversion between lat/long/height, SPC, UTM, XYZ, and USNG systems. NCAT currently uses NADCON* to perform three-dimensional (latitude, longitude, ellipsoid height) coordinate transformations and VERTCON* to perform orthometric height transformations.

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6. www.fema.gov › sites › defaultGuidance for Flood Risk Analysis and Mapping - FEMA.gov

   www.fema.gov › sites › default

   execution of vertical datum conversions from the National Geodetic Vertical Datum of 1929 (NGVD29) to the North American Vertical Datum of (NAVD88), and provides context and supporting guidance for the efficient implementation of those standards, as well as several scenariobased examples to -