ESRI staff and industry users are now documenting the best procedures to download, convert, load, and model DLG data from the USGS site. The paper will be available on ESRI's mining Web site. Here is a brief description of DLG data acquisition, conversion, and modeling. DLG files are created in a UTM projection using the NAD 27 datum and the Clarke 1866 ellipsoid. Horizontal and vertical units of measure are metric.
Data are available at several scales and formats.
Each tile includes five to seven related files containing the vector data listed above. DLG data are downloaded in a zipped GZ format and must be extracted by the user. Individual file names are long and confusing. Data files are best renamed as they are downloaded and unzipped. The SME paper available at the ESRI Web site will explain file downloading, extraction, and preferred file naming conventions.