Illinois, Indiana, and Ohio Magnetic and Gravity Maps and Data: A Website for Distribution of Data David L. Daniels, Robert P. Kucks, and Patricia L. Hill USGS Data Series 321 README.txt FILE FOR GRIDDED AND IMAGE DATA TRANSFER DIRECTORY These grids are presented in Geosoft Oasis montaj (proprietary software) binary format, with two files describing each of the grids (suffixes .grd and .grd.gi). The .gi file contains information about the projection used by the software. This grid format can be converted to numerous other formats using the downloadable free software offered by Geosoft at (look for download link). Also included are Arcview geo-referenced .tif files and accompanying .tfw world files for use in digital overlay needs. Below is the projection information for each grid and image as defined in the above formats. ---------------------------------------------------------- Projection Lambert Conformal Conic Parameters: 1st standard parallel 33 0 0.000 2nd standard parallel 45 0 0.000 central meridian -83 0 0.00 latitude of projection's origin 0 0 0.000 false easting (meters) 0.00000 false northing (meters) 0.00000 ----------------------------------------------------------------- Disclaimer. This database, identified as DS 321 has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is subsequently complete, the USGS reserves the right to revise the data persuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.