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Gravity and Magnetics Research
ONLINE GRAVITY DATA SET for the lower 48 states
NORTH AMERICAN GRAVITY DATABASE EFFORT:
The obvious next step after the U. S. gravity database and North American Magnetic Map efforts is an improved regional gravity database for North America. Thus, an international effort by governmental agencies, universities, professional organizations, and private industry is underway to update the publicly available North American Gravity Database. The current database that was released roughly two decades ago needs revision to improve its overall quality, coverage, observation density, and versatility. Considerable data have been made available in the intervening period and improvements are possible in the calculation of gravity anomalies by taking advantage of available terrain and geodetic models and high-speed data processing procedures and facilities. Data will be made available in a web-based system as part of the U. S. Geoinformatics program and through other governmental agencies.
The database will have a comprehensive menu making it useful for those with differing scientific interests and backgrounds. The user will be able to select desired corrections to the gravity data, units used, datums employed, and type of gravity anomaly and retrieve information on the predicted errors in the data. The default gravity anomalies (in milligals) of the database based on internationally accepted datums and constants will be useful for geological studies and most geophysical investigations. Database fields and formats will accommodate the increasingly available high-resolution, airborne, satellite, marine, and gradient gravity data and will be updated as additional data are obtained and improvements are made in data processing. The database will be updated as additional data are obtained and improvements are made in data processing.
Click on the link below to see an initial report from the Standards /Format Working Group, of the North American Gravity Database Committee. Standards/Format Working Group Final Report
Magnetic Anomaly Map of North America Project
Aeromagnetic data is a fundamental data layer for integrated studies in which other spatial data such as gravity, Landsat images, digital elevation models, geologic maps, and seismic tomography form layers. The U. S. Geological Survey has prepared a brief document (Introduction to Potential Fields: Magnetics) for those interesting in learning more about this technique.
The UTEP group has worked to aid efforts to compile aeromagnetic data in southwestern North America. This effort has been conducted in close cooperation with the U. S. Geological Survey and Mexican colleagues. There is has been a concerted effort on the part of the U. S. Geological Survey to construct an aeromagnetic compilation for the U. S., which was, in turn, used in a companion effort to compile a database for North America. We have sent all of our data to the U. S. Geological Survey for use in these compilations, which are now complete. To quote from their website, "The data sets that make up the current U.S. national data base (more than 1,000 individual surveys, including offshore data to 320 km) will be standardized to a consistent ASCII format".
This project is described in detail at the North American Magnetic Map project website at: http://crustal.usgs.gov/namad/, and booklet describing the project and a page-sized copy of the map can also be downloaded at this site.
The digital grids that were prepared are described at http://pubs.usgs.gov/of/2002/ofr-02-414/ and can downloaded at that site.
In addition, individual compilations for many states and for numerous individual separate surveys can be found at http://crustal.usgs.gov/projects/namad/us_digital_data.html.
Those interested in a relatively small area that is solely contained within a single state or an area covered by a specific survey, should consider using these data directly in order to obtain maximum resolution. These data are distributed in various grid formats.
ONLINE MAGNETIC DATA SET
As part of the GEON effort, we have prepared a version of the North American Magnetic Map grid that is searchable by latitude and longitude. Thus individuals wanted to use these valuable data can easily download only the section of the grid of interest to them in a simple ASCII format. In order to make the gird searchable, we attached a latitude and longitude (NAD27) to each data point. Thus, the data are basically individual points like our accompanying gravity data set. This approach makes it easy to make matching gravity and magnetic maps but does require that the user regrid the data make a contour map.
CLICK HERE- GeoNet North American Magnetic Database -CLICK HERE
The data set for Texas and environs
The only product that we have produced that is not readily available from the U. S. Geological Survey is an edited and carefully merged version of the original flight line data for the National Uranium Resource Evaluation (NURE) program for the State of Texas and adjacent areas. These data are idea for computer modeling and analytical calculations such as depth to basement estimation efforts, because they have not been interpolated as part of a gridding algorithm. This data set is available by simply requesting it via email to:
There is an initiative underway to improve the U. S. aeromagnetic database via a high altitude aeromagnetic survey. Magnetic anomalies reveal much about the composition, structural architecture, and even thermal regime of a region. Thus, a high quality aeromagnetic data set is a fundamental data layer for integrated studies in which other spatial data such as gravity, Landsat images, digital elevation models, geologic maps, and seismic tomography form layers. The need for a much-improved aeromagnetic database for North America has been recognized for many years, and legacy low-altitude aeromagnetic data have just been complied into a data set for North America. However, there is a strong need for a high-altitude survey to both serve as a mechanism to stitch the low-altitude data together properly and to provide long wavelength data that are of considerable significance and utility in their own right. Recently a broad cross-section of the geomagnetic community held a workshop because of an exciting and cost-effective opportunity to collect invaluable magnetic anomaly data during a mission over the U.S. in the near future (Open-File Report 2002-366).