Mexico Geoid Heights (MEXICO97)

Metadata Updated: November 12, 2020

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.

Access & Use Information

License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Dates

Metadata Date September 25, 2017
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Reference Date(s) January 1, 1999 (publication)
Frequency Of Update irregular

Metadata Source

Harvested from NGDC MGG Geophysics

Additional Metadata

Resource Type Dataset
Metadata Date September 25, 2017
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Reference Date(s) January 1, 1999 (publication)
Responsible Party NOAA National Centers for Environmental Information (Point of Contact)
Contact Email
Guid gov.noaa.ngdc.mgg.geophysics:G01433
Access Constraints Distribution liability: NOAA and NCEI make no warranty, expressed or implied, regarding these data, nor does the fact of distribution constitute such a warranty. NOAA and NCEI cannot assume liability for any damages caused by any errors or omissions in these data. If appropriate, NCEI can only certify that the data it distributes are an authentic copy of the records that were accepted for inclusion in the NCEI archives., Use Constraints: If you use this data, please cite the National Geophysical Data Center and the originator of the data., Access Constraints: None
Bbox East Long -75
Bbox North Lat 33
Bbox South Lat 14
Bbox West Long -119
Coupled Resource
Frequency Of Update irregular
Licence
Metadata Language eng; USA
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System urn:ogc:def:crs:EPSG::5715
Spatial Harvester True

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