Digital data grids for the magnetic anomaly map of North America.

Dataset Identification:

Resource Abstract:
description: A digital magnetic anomaly database and map for the North American continent is the result of a joint effort by the Geological Survey of Canada (GSC), U. S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM). The database and map represent a substantial upgrade from the previous compilation of magnetic anomaly data for North America, now over a decade old. This report presents three unique, gridded data sets used to make the magnetic anomaly map of North America. All three grids have 1-km spacing and are projected to the DNAG projection. These grids are provided in Geosoft binary grid format, with two files describing each of the grids (suffixes .grd and .gi). The first grids (NAmag_origmrg.grd and USmag_origmrg.grd) show the magnetic field at 1,000 m. above terrain. For the second grids (NAmag_hp500.grd and USmag_hp500.grd) we removed long-wavelength anomalies (500 km and greater) from the first grid. This grid was used for the published map. Although the North American merged grid represents a significant upgrade to older compilations, the existing patchwork of surveys is inherently unable to accurately represent anomalies with long (greater than roughly 150 km) wavelengths, particularly in the US and Canada (U.S. Magnetic- Anomaly Data Set Task Group, 1994). The lack of information about long wavelength anomalies is primarily related to datum shifts between merged surveys, caused by data acquisition at widely different times and by differences in merging procedures. Therefore, we removed anomalies with wavelengths greater than 500 km from the merged grid to reduce the effects caused by the spurious long wavelengths but still maintain the continuity of anomalies. The correction was accomplished by transforming the merged grid to the frequency domain, filtering the transformed data with a long-wavelength cutoff at 500 km, and subtracting the long-wavelength data grid from the merged grid. In addition to the 500-km high pass filter, an equivalent source method, based on long-wavelength characterization using satellite data (CHAMP satellite anomalies, Maus and others, 2002), was also used to correct for spurious shifts in the original magnetic anomaly grid (Ravat and others, 2002). These results are presented in the third grids (NAmag_CM.grd and USmag_CM.grd), in which the wavelengths longer than 500 km have been replaced by downward-continued satellite data.; abstract: A digital magnetic anomaly database and map for the North American continent is the result of a joint effort by the Geological Survey of Canada (GSC), U. S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM). The database and map represent a substantial upgrade from the previous compilation of magnetic anomaly data for North America, now over a decade old. This report presents three unique, gridded data sets used to make the magnetic anomaly map of North America. All three grids have 1-km spacing and are projected to the DNAG projection. These grids are provided in Geosoft binary grid format, with two files describing each of the grids (suffixes .grd and .gi). The first grids (NAmag_origmrg.grd and USmag_origmrg.grd) show the magnetic field at 1,000 m. above terrain. For the second grids (NAmag_hp500.grd and USmag_hp500.grd) we removed long-wavelength anomalies (500 km and greater) from the first grid. This grid was used for the published map. Although the North American merged grid represents a significant upgrade to older compilations, the existing patchwork of surveys is inherently unable to accurately represent anomalies with long (greater than roughly 150 km) wavelengths, particularly in the US and Canada (U.S. Magnetic- Anomaly Data Set Task Group, 1994). The lack of information about long wavelength anomalies is primarily related to datum shifts between merged surveys, caused by data acquisition at widely different times and by differences in merging procedures. Therefore, we removed anomalies with wavelengths greater than 500 km from the merged grid to reduce the effects caused by the spurious long wavelengths but still maintain the continuity of anomalies. The correction was accomplished by transforming the merged grid to the frequency domain, filtering the transformed data with a long-wavelength cutoff at 500 km, and subtracting the long-wavelength data grid from the merged grid. In addition to the 500-km high pass filter, an equivalent source method, based on long-wavelength characterization using satellite data (CHAMP satellite anomalies, Maus and others, 2002), was also used to correct for spurious shifts in the original magnetic anomaly grid (Ravat and others, 2002). These results are presented in the third grids (NAmag_CM.grd and USmag_CM.grd), in which the wavelengths longer than 500 km have been replaced by downward-continued satellite data.
Citation
Title Digital data grids for the magnetic anomaly map of North America.
creation  Date   2018-06-08T07:37:57.345139
Resource language: 
Processing environment:  
Back to top:

Resource distribution information

Digital Transfer Options
Linkage for online resource
name Dublin Core references URL
URL: http://pubs.usgs.gov/of/2002/ofr-02-414/
protocol WWW:LINK-1.0-http--link
link function information
Description URL provided in Dublin Core references element.
Linkage for online resource
name Dublin Core references URL
URL: http://pubs.usgs.gov/sm/mag_map/
protocol WWW:LINK-1.0-http--link
link function information
Description URL provided in Dublin Core references element.
Linkage for online resource
name Dublin Core references URL
URL: http://pubs.usgs.gov/of/2002/ofr-02-361/
protocol WWW:LINK-1.0-http--link
link function information
Description URL provided in Dublin Core references element.
Linkage for online resource
name Dublin Core references URL
URL: http://pubs.usgs.gov/of/1999/ofr-99-0557/html/mag_home.htm
protocol WWW:LINK-1.0-http--link
link function information
Description URL provided in Dublin Core references element.

Metadata data stamp:  2018-08-06T19:37:59Z
Resource Maintenance Information
maintenance or update frequency: 
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 2018-08-06T19:37:59Z
Metadata contact - pointOfContact
organisation Name  CINERGI Metadata catalog
Contact information
Address
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:5c26be68-3ca3-4520-a98b-a6ebd25015a6

Metadata record format is ISO19139 XML (MD_Metadata)