Dataset Identification:
Resource Abstract:
- description: This 2' geoid height grid for Mexico, and North-Central America, is the MEXICO97 geoid model. The computation
used about one million terrestrial and marine gravity measurements held in the NGS database as of March 1997. These gravity
measurements were augmented by data contributions from NGA (former National Imagery and Mapping Agency), and satellite altimeter-derived
gravity anomalies computed by Sandwell and Smith (1997). Large data gaps south of 20 degrees North latitude were filled with
15'x15' gravity values derived from the EGM96 global geopotential model. This helped control interpolation errors
across the data gaps during the gridding of terrain corrected Bouguer anomalies. After gridding of the Bouguer anomalies,
the Bouguer plate was restored, a degree 360 model of gravity anomalies (from EGM96) was removed, and the residual free-air
anomalies in the data gaps (south of 20 degrees North Latitude) were zeroed. (This zeroing was found to be the best way currently
available to yield a reasonable geoid in the data gaps). The residual Faye anomalies were converted to residual co-geoid undulations
through a 1-D FFT formulation of Stokes' integral, and finally the EGM96 undulation model was restored, and the indirect
effect applied. This means that in the data gaps, long wavelength information is provided by EGM96, short wavelength information
is provided by the 2'x2' DTED (during the application of the indirect effect), but medium wavelength information
(usually provided by gravity measurements) is missing altogether. Although the exact accuracy of the geoid in the data gaps
is difficult to ascertain, the quoted accuracy for EGM96 (which is the primary source of geoid information in the data gaps)
is below 50 cm in these areas. The gravity values are based on the International Gravity Standardization Net 1971 (IGSN71).
The geoid heights are referred to the Geodetic Reference System 1980 (GRS80) ellipsoid, centered at the origin of the International
Terrestrial Reference Frame 1994 (ITRF94(1996.0)). Additional information is available at: http://www.ngs.noaa.gov/GEOID/MEXICO97/
We are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.;
abstract: This 2' geoid height grid for Mexico, and North-Central America, is the MEXICO97 geoid model. The computation
used about one million terrestrial and marine gravity measurements held in the NGS database as of March 1997. These gravity
measurements were augmented by data contributions from NGA (former National Imagery and Mapping Agency), and satellite altimeter-derived
gravity anomalies computed by Sandwell and Smith (1997). Large data gaps south of 20 degrees North latitude were filled with
15'x15' gravity values derived from the EGM96 global geopotential model. This helped control interpolation errors
across the data gaps during the gridding of terrain corrected Bouguer anomalies. After gridding of the Bouguer anomalies,
the Bouguer plate was restored, a degree 360 model of gravity anomalies (from EGM96) was removed, and the residual free-air
anomalies in the data gaps (south of 20 degrees North Latitude) were zeroed. (This zeroing was found to be the best way currently
available to yield a reasonable geoid in the data gaps). The residual Faye anomalies were converted to residual co-geoid undulations
through a 1-D FFT formulation of Stokes' integral, and finally the EGM96 undulation model was restored, and the indirect
effect applied. This means that in the data gaps, long wavelength information is provided by EGM96, short wavelength information
is provided by the 2'x2' DTED (during the application of the indirect effect), but medium wavelength information
(usually provided by gravity measurements) is missing altogether. Although the exact accuracy of the geoid in the data gaps
is difficult to ascertain, the quoted accuracy for EGM96 (which is the primary source of geoid information in the data gaps)
is below 50 cm in these areas. The gravity values are based on the International Gravity Standardization Net 1971 (IGSN71).
The geoid heights are referred to the Geodetic Reference System 1980 (GRS80) ellipsoid, centered at the origin of the International
Terrestrial Reference Frame 1994 (ITRF94(1996.0)). Additional information is available at: http://www.ngs.noaa.gov/GEOID/MEXICO97/
We are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.
Citation
- Title Mexico Geoid Heights (MEXICO97).
-
- creation Date
2018-02-08T06:35:36.773327
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Metadata data stamp:
2018-08-06T21:44:40Z
Resource Maintenance Information
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- notes: This metadata record was generated by an xslt transformation from a dc metadata record; Transform by Stephen M. Richard, based
on a transform by Damian Ulbricht. Run on 2018-08-06T21:44:40Z
Metadata contact
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pointOfContact
- organisation Name
CINERGI Metadata catalog
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- Contact information
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- Address
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- electronic Mail Address cinergi@sdsc.edu
Metadata language
eng
Metadata character set encoding:
utf8
Metadata standard for this record:
ISO 19139 Geographic Information - Metadata - Implementation Specification
standard version:
2007
Metadata record identifier:
urn:dciso:metadataabout:67472d2d-e78d-48ed-98b2-4980c858bf37
Metadata record format is ISO19139 XML (MD_Metadata)