The U.S. Geological Survey National Geospatial Program is now in the process of scanning an estimated 250,000 printed topographic map quadrangles that have been archived since the inception of the program in 1884. The reason for the estimated quantity is that no full set exists, and no database existed to keep track of all the maps. Each map is being scanned at 600 pixels to the inch, and all will be georeferenced to facilitate change detection.
The project serves to safeguard the archive in the USGS Reston Map Library from fire or flood, as well as to make this content available to the public. The maps will be made available for viewing and downloading from the National Map Viewer in GeoPDF and GeoTIFF formats at full resolution with the GIS professional in mind. The sheet details, including collars with full metadata, will be preserved and there will be a version where the collar can easily be masked for mosaicing.
There is great care being taken to preserve every data element of the maps. The USGS is working with Library of Congress and sharing the same Oracle database to create a catalog and metadata for all topographic maps published. The metadata captured includes the primary state of the map, photo inspection, datum, projection, scale, and other publishers (such as the War Department or U.S. Army Corps of Engineers).
The process uses the automated georeferencing Quad-G software developed by the University of Wisconsin, Madison. The maps are being run in batches with approximately 1,000 maps scanned per day since the January start date. There is then some manual mode and quality assurance checks, with special attention taken to non-conforming and custom maps.
The release of these archived maps will follow the roll-out of the US TOPO, with the State of Kansas as the first, with entire states released one at a time. Maps will be made available beginning in mid-2011.