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  1. The grids in VERTCON 3.0 release 20190601 are replacements for those in VERTCON 2.1, which transformed only between NGVD 29 and NAVD 88 for CONUS. However VERTCON is no longer the name of a stand-alone transformation tool.

  2. 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.

  3. Nov 4, 2020 · HEIGHT DIFFERENCES BETWEEN NAVD 88 AND NGVD 29 IN CONTERMINOUS UNITED STATES; UNITS = CM (NOAA) According to the NGS website, surveyors used a method called Differential or Spirit Leveling, where a rod is held on a mark with a known elevation. “A reading is taken on the rod, which provides the elevation of the line-of-sight through the ...

  4. 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.

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  5. Mar 28, 2024 · Once the page comes up, please select horizontal+height from the top row. Select orthometric from the third row. Enter your latitude, longitude and orthometric height. Towards the bottom of the screen you see an option to choose an input geopotential or vertical datum. Pick NGVD 29 from the dropdown and click submit.

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  7. document contains the following information about conversion from NGVD 29 to NAVD 88: General information about the two vertical datums most commonly used by FEMA for referencing 1-percent-annual-chance flood elevation information in Flood Insurance Rate Map (FIRM)

  8. METHOD Program VERTCON computes the modeled difference in orthometric height between the North American Vertical Datum of 1988 (NAVD 88) and the National Geodetic Vertical Datum of 1929 (NGVD 29) for a given location specified by latitude and longitude. The VERTCON 2.0 model was computed on May 5, 1994 using 381,833 datum difference values.

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