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Open-File Report 99–527

Aeromagnetic Surveying in Wisconsin 1998-99: Digital Data Files

By Robert E. Bracken and Suzanne W. Nicholson

with Logistics Report, by High-Sense Geophysics Limited

Thumbnail aeromagnetic map, southern Wisconsin


This report contains digital data, image files, and text files describing the data formats and survey procedures for aeromagnetic data collected in the southern one-third of Wisconsin during 1998-1999.

Over the past 12 years the U.S. Geological Survey has conducted a series of aeromagnetic surveys in Wisconsin aimed at completing the coverage of high-quality, moderate-resolution aeromagnetic surveying in the State. The data from these surveys have proven to be an effective tool for delineating structures in the Precambrian basement in Wisconsin and have been useful in the study of the mineral resources in the region. Precambrian basement rocks rarely crop out in this region because of glacial deposits and Paleozoic sedimentary cover rocks. Surveys by the U.S. Geological Survey (USGS) in 1988 (Hittleman and others, 1992), 1996 (Snyder, 1998), and 1997 (Daniels and others, 1998) have closed gaps in the aeromagnetic coverage of the Midcontinent rift area, adjacent to Minnesota.

The most recent survey flown in 1998-99 is the focus of this report. It extends aeromagnetic coverage southwards to the bottom of the State. This report releases the digital data for that survey. Both digital flight-line and gridded data are included as well as images of the gridded magnetic data presented as one contiguous map. Facts about this survey and parameters for the digital files are given.


All the available digital data in line and gridded data formats are contained within the following subdirectories of the data folder.
Contains the final leveled magnetic data and the radar altitude data in gridded form as supplied by the contractor. The magnetic grids have been translated to various formats.
Contains all of the basic flight line data. The original 1/10-second line-data files, supplied by the contractor, are included in a compressed form (extraction software is included). Also, 1-second winnowed line-data files are included in the original ASCII format.
Contains USGS software for potential-field geophysical-data processing on a PC computer. (This software directly uses the .sf grid supplied in the grid subfolder and can also manipulate point data found in the line subfolder after it has been converted to an accepted format).

Posted online October 28, 2009
CD originally published in 1999

For additional information contact:

Eastern Region Minerals

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Bracken, R.E., and Nicholson, S.W., 1999, Aeromagnetic surveying in Wisconsin 1998-99 -- Digital data files: U.S. Geological Survey Open-File Report 99-527, available online only.

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