VDatum is a tool developed by the Office of Coast Survey for the transformation of elevation data from one vertical datum into another. Such transformations are necessary when data from diverse sources are to be combined or compared. Artificial steps or discontinuties can appear in maps and charts if they are built from data based on inconsistent datums. This problem can be particularly acute in coastal areas.

VDatum converts elevation data between tidal, orthometric, and ellipsoidal vertical datums, allowing users to establish a common reference system for all elevation data sets. VDatum is unique since it is based on a hydrodynamic model to convert between tidal and orthometric datums.

Features

• Transforms geospatial data among a variety of vertical datums (i.e., tidal, ellipsoidal, and orthometric datums)
• Transforms geospatial data among horizontal datums
• Supports conversion using several geoid models
• Converts between the National Geodetic Vertical Datum (NGVD) of 1929 and the North American Vertical Datum (NAVD) of 1988 using VERTCON
• Supports conversions between the International Great Lakes Datum (IGLD) of 1985 and NAVD88

Data Requirements

Elevation data – point data (ASCII) in geographic coordinates (latitude and longitude) and Universal Transverse Mercator (UTM) coordinates

Support

This User Guide contains a step-by-step guide to the operation of the VDatum software

VDatum is a NOS Tool. You can access VDatum at this URL:

http://vdatum.noaa.gov/download.html

Disclaimer: Although many of the vertical datum transformations between the North American Vertical Datum of 1988 (NAVD 88) and mean sea level, and between mean sea level and the other tidal datums, are based on tidal values from the present National Tidal Datum Epoch (NTDE, 1983 to 2001), some are based on data from older tidal epochs. NOS is in the process of updating the data in VDatum to conform to the latest NTDE. In the meantime, care should be used when applying these transformations. 

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