Open-File Report 99-028
Aeromagnetic Surveying in Wisconsin 1997-98: Digital Data Files 
By David L. Daniels, Suzanne W. Nicholson, and William F. Cannon

Directory "data"

The basic survey measurements are in five ASCII files (file extension .dat)
derived from the original contractor files. Each record of each file
contains 15 fields of data per measurement, at a sampling interval
of one second. USGS style DOS binary point files (.pos) with 9 fields
are also given. Files are compressed type.  Download either
the separate files or the compressed files.