Gridded Aeromagnetic Files - README The files in this directory contain magnetic anomaly values (ntesla) for the western United States on a state by state basis. The original source of this data was the DNAG magnetics grid on the Geophysics of North America CD-ROM (out of print). The data have since been reformatted into approximately four degree latitude strips and put on the NGDC web site. We took these data, merged strips, and windowed out data centered on each individual state (lower 48) in the NAVDAT study area. There is approximately one degree of extra data padding each edge of the state, to allow for later processing, merging without state line faults, etc. The data are in X,Y,Z ascii format, so they can be read into virtually any package. They are still gridded, however, at a 2.5 minute interval. The X is longitude, the Y is latitude, and the Z is the magnetic anomaly value. These can be easily read into such packages as ArcView (as a Table, then converted to a shapefile using Add Event Theme), or Excel (just open the file), or MatLab (using fscanf one line at a time, or textread). For the first two applications, you may want to add a line at the top of the ascii file: X Y Z To label your table columns.