The NGS GEOID Page
Last updated 2009/10/01
The National Geodetic Survey has released updated models for transforming heights between ellipsoidal coordinates and more physical height systems that relate to water flow. These models cover all regions including the conterminous United States (CONUS), Alaska, Hawaii, Guam and the Commonwealth of the Northern Mariana Islands, and American Samoa. Models for Puerto Rico and the U.S. Virgin Islands are being held back pending release of final control data for the USVI but will likely be released later this Fall. GEOID09 transforms to NAVD 88 in CONUS and Alaska and to the respective datums for all the other regions (each having its own datum point). Models for the Deflection of the Vertical have also been released for these same regions mainly for aid in navigation systems.
Latest models
Hybrid Geoids - Converts heights from NAD 83 to regional Vertical datums (e.g., NAVD 88 for CONUS)
Gravimetric Geoids - Converts heights from ITRFxx to the NGS geoid surface (not NAVD 88 or other Vertical datums)
Vertical Deflection Models
- USDOV2009 based on the 2009 gravimetric model
- Release of DEFLEC09 data files (based on the 2009 hybrid model) are pending
- DEFLEC09 BETA release - data models not for production
- DEFLEC99
- DEFLEC96
What is the geoid?(Definition, History) |
What is a deflection
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GRAV-D |
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Geoid Links(Agencies, Models) |
Research Links(Projects at least loosely tied to the geoid) |
North American Geoid
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Online papers about the geoid |
Who uses the geoid?(Studies with NGS geoid models) |
NGS geoid research software |
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Have a question?