|Description||Aeromagnetic surveys of Illinois, Indiana, and Ohio, merged to form seamless grids across the state. Gravity anomaly data are provided as well.|
|Originators||Daniels, David L.; Kucks, Robert P.; and Hill, Patricia L.|
|Publication||U.S. Geological Survey Data Series 321|
Aeromagnetic anomaly grid cells are given in nanoteslas, and values are expected to range from -400 to 400. Gravity anomaly grid cells are given in milligals. Values are expected to range from -64 to 0 for complete Bouguer anomaly and from -40 to 20 for isostatic anomaly. Grids are provided in Geosoft's binary (proprietary) format with georeference information stored in an ancillary file and as TIFF images with georeference transformation information stored in an ancillary .tfw "world" file.