Data

USGS DLG files must be translated into DXF before AutoCAD can read the files. Here is one way this can be accomplished: Download a DLG to DXF converter. There are different versions of this program depending on the version of AutoCAD. DLGTODXF -...
That depends on what kind of reprojection you want to do. In some cases, if you want to reproject from one datum to another (specifically NAD 27 to NAD 83 or NAD 83 to NAD 27), a simple xy shift will suffice. This shift will not introduce measurable...
Data are offered in both compressed ARC workspaces and compressed SDTS transfer format.  
It will probably take approximately 5 years to digitize the archive. A priority scheme is being developed and will be made available to the public at a later date.
Digital elevation model (DEM) data are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals...
A digital orthophoto quadrangle (DOQ) is a computer-generated image of an aerial photograph in which displacements caused by terrain relief and camera tilts have been removed. It combines the image characteristics of a photograph with the geometric...
A DRG is a scanned image of a U.S. Geological Survey (USGS) topographic map. The scanned image includes all map collar information. The image inside the map neatline is georeferenced to the surface of the Earth. DRG Fact Sheet  
SDTS transfers are the data sets used to exchange spatial data between different computer systems. SDTS transfers consist of a series of modules (the SDTS's logical grouping of related data) encoded into files using ISO 8211 standard, 'Specification for...
SDTS is the acronym for the Spatial Data Transfer Standard. SDTS is a FIPS(173) and FGDC (STD-002) standard that defines a non-proprietary format for packaging vector or raster spatial data with attributes, metadata, a data quality report and usually a...
It's a combination of USGS hydrologic digital line graph files and EPA reach files, version 3.0 (RF3). The USGS files are used for spatial accuracy and the EPA files are used for attribute information.