Geoid Height and Deflections of the Vertical Models - National Geospatial Data Asset (NGDA) Geoid Models
National Geodetic Survey
Data Set
(DS)
| ID: 39739
| Published / External
Created: 2017-04-05
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Last Modified: 2023-09-01
Project (PRJ) | ID: 37223
ID: 39739
Data Set (DS)
* Discovery• First Pass
» Metadata Rubric
Item Identification
* » Title | Geoid Height and Deflections of the Vertical Models - National Geospatial Data Asset (NGDA) Geoid Models |
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Short Name | GeoidModels |
* Status | Completed |
Creation Date | 1996 |
Revision Date | 2018 |
• Publication Date | 2013 |
* » Abstract |
In Gauss' words, the geoid is "the mathematical figure of the Earth". This figure is an equipotential surface coincident with the idealized mean sea surface. The geoid can be computed from the geodetic boundary value problems that use gravity data as its boundary value. A geoid model computed using gravity data is called gravimetric geoid. On the other hand, geoid height at bench marks can also be computed using data of the spirit leveling and the Global Positioning System (GPS). A geoid model that fixed to the GPS/leveling data is called hybrid geoid. Both geoid models can serve as the zero-height-surface of a country's height system by selection. To satisfy this need, National Geodetic Survey has published a series of geoid models (http://geodesy.noaa.gov/GEOID). The latest models are USGG2012 and GEOID12B, both are at 1 arc-second grids over the territory of the United States. |
* Purpose |
GEOID12B is used to convert the ellipsoidal height acquired by the Global Positioning System (GPS) in NAD 83 into an NAVD 88 orthometric height-the datum used in many maps and charts and other applications. USGG12 is computed using gravity data and can be used for circulation studies and other applications. |
Notes |
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Other Citation Details | |
• Supplemental Information |
USGG2012 is a gravimetric model that refers to the Geodetic Reference System 1980 (GRS80) while the hybrid model GEOID12B is fixed to the GPS/leveling data at bench marks of the North America Vertical Datum 1988 (NAVD88) - the official US height system. Therefore, GEOID12B converts the ellipsoidal height of GPS into the official NAVD88 orthometric height. More specific, GEOID12B converts the ellipsoidal height in the North American Datum of 1983 (NAD 83 [2011.0]) into orthometric height in the NAVD 88 for the conterminous United States and Alaska. In regions where there is no NAVD88, GEOID12B converts the ellipsoidal height in NAD 83 (PA11) into the local vertical datums in Hawaii and American Samoa. The ellipsoidal height in NAD 83 (MA11) can also be converted to heights of the local vertical datums in Guam and the Commonwealth of the Northern Mariana Islands by using GEOID12B.
USDOV2012 and DEFLEC12B are Deflection of the Vertical models that describe the angular difference between the norm of the zero-height-surfaces and the norm of the reference ellipsoid. USDOV2012 was computed from USGG2012, whereas DEFLEC12B was determined from GEOID12B. Both are given 1 arc-second grids.
NGS offers technical information of the geoid models and practical information concerning its use on the NGS website at http://geodesy.noaa.gov/GEOID. NGS also offers a workshop concerning GPS-derived heights and the use of the geoid models to convert from GPS-derived heights to orthometric heights (see http://geodesy.noaa.gov/PC_PROD/WorkShops/). NAVD 88 coverage in Alaska is incomplete and may not be suitable for all regions. Notice that Hawaii, Guam, CNMI, American Samoa, Puerto Rico (PR), and the U.S. Virgin Islands (VI) all have their own separate vertical datums distinct from NAVD 88. GEOID12B converts between the appropriate local version of NAD 83 and the respective vertical datums for each of these regions. The GEOID12B product comprises eight files for the conterminous United States: four files for Alaska, and one each for Hawaii, PR/VI, American Samoa, and Guam/CNMI. Single grids also are available for CONUS and Alaska. Each file contains geoid heights on a one-minute by one-minute grid in both big-endian and little-endian binary (PC compatible) formats. The INTG program is supplied at the download site to interpolate to a specific position within these grids. Another program, XNTG, is supplied to extract subsets and convert the grids between ASCII and binary. Both are in FORTRAN, are available compiled and as source code, and can byte-swap the grids if needed on a Unix platform. There is also an on-line geoid computational facility within the NGS Geodetic Tool Kit at http://www.ngs.noaa.gov/TOOLS. Similar files, programs, and on-line computational facilities exist for USGG2012, USDOV2012 and DEFLEC12B. |
DOI (Digital Object Identifier) | |
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Keywords
Theme Keywords
Thesaurus | Keyword |
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ISO 19115 Topic Category | location |
NGDA Portfolio Themes | Geodetic Control Theme |
NGDA Portfolio Themes | National Geospatial Data Asset |
NGDA Portfolio Themes | NGDA |
None | DEFLEC12A |
None | EGM2008 |
None | Elevation |
None | Geodesy |
None | Geodetic/Global Positioning |
None | GEOID03 |
None | GEOID12A |
None | Gravity Fields |
None | INTERIOR AND CRUST |
None | LAND |
None | Terrain Elevation |
None | Topographic Data |
None | USGG2012 |
Temporal Keywords
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* Spatial Keywords
Thesaurus | Keyword |
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None | Alaska |
None | American Samoa |
None | Caribbean |
None | Commonwealth of the Northern Mariana Islands |
None | Guam |
None | Hawaii |
None | Mexico |
None | Puerto Rico |
None | United States |
None | Virgin Islands |
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Physical Location
• » Organization | National Geodetic Survey |
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• » City | Silver Spring |
• » State/Province | MD |
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Data Set Information
* Data Set Scope Code | Data Set |
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Maintenance Note |
Possibly 2015 or later depending on changes in control data in the NGS database. |
» Data Presentation Form | model |
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Distribution Liability |
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Support Roles
* » Support Role | Data Steward |
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* » Date Effective From | 2013 |
Date Effective To | |
Organization | NGS Communications and Outreach Branch |
Email Address | ngs.infocenter@noaa.gov |
Phone | (301) 713-3242 |
Fax | (301) 713-4172 |
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Contact Instructions |
* » Support Role | Distributor |
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* » Date Effective From | 2013 |
Date Effective To | |
Organization | NGS Communications and Outreach Branch |
Email Address | ngs.infocenter@noaa.gov |
Phone | (301) 713-3242 |
Fax | (301) 713-4172 |
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URL | |
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* » Support Role | Metadata Contact |
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* » Date Effective From | 2013 |
Date Effective To | |
Organization | NGS Communications and Outreach Branch |
Email Address | ngs.infocenter@noaa.gov |
Phone | (301) 713-3242 |
Fax | (301) 713-4172 |
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* » Support Role | Point of Contact |
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* » Date Effective From | 2013 |
Date Effective To | |
Organization | NGS Communications and Outreach Branch |
Email Address | ngs.infocenter@noaa.gov |
Phone | (301) 713-3242 |
Fax | (301) 713-4172 |
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Currentness Reference | Publication Date |
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* » W° Bound | -175 |
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* » E° Bound | -63 |
* » N° Bound | 71 |
* » S° Bound | 15 |
* » Description |
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Extent Group 1 / Time Frame 1
* » Time Frame Type | Discrete |
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* » Start | 2012 |
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Reference Systems
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EPSG Code | EPSG:4269 | ||||||||||||||||||||||||||||
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EPSG Code | EPSG:5703 | ||||||||||||||||||||||||||||
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* » Security Class | Unclassified |
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• » Data Access Constraints |
none |
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» Download URL | http://www.ngs.noaa.gov/GEOID/// |
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File Type (Deprecated) | programs for PC or UNIX |
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URLs
URL | http://www.ngs.noaa.gov/GEOID// |
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URL Type | Online Resource |
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Activity Log
Activity Time | 2015-08-27 |
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Date that the source FGDC record was last modified. |
Activity Time | 2017-04-05 |
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Description |
Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details. |
Activity Time | 2017-08-14 |
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Partial upload of Maintenance Note field only. |
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» Do these Data Comply with the Data Access Directive? | |
» Is Access to the Data Limited Based on an Approved Waiver? | |
» If Distributor (Data Hosting Service) is Needed, Please Indicate | |
» Approximate Delay Between Data Collection and Dissemination | |
» If Delay is Longer than Latency of Automated Processing, Indicate Under What Authority Data Access is Delayed |
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» Actual or Planned Long-Term Data Archive Location | |
» If World Data Center or Other, Specify | |
» If To Be Determined, Unable to Archive, or No Archiving Intended, Explain |
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» How Will the Data Be Protected from Accidental or Malicious Modification or Deletion Prior to Receipt by the Archive? |
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Child Items
Rubric scores updated every 15m
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Catalog Details
Catalog Item ID | 39739 |
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Metadata Record Created By | Tyler Christensen |
Metadata Record Created | 2017-04-05 13:07+0000 |
Metadata Record Last Modified By | Brianna Key |
» Metadata Record Last Modified | 2023-09-01 15:26+0000 |
Metadata Record Published | 2017-08-14 |
Owner Org | NGS |
Metadata Publication Status | Published Externally |
Do Not Publish? | N |
Metadata Workflow State | Published / External |
Metadata Last Review Date | 2017-08-14 |
Metadata Review Frequency | 1 Year |
Metadata Next Review Date | 2018-08-14 |
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