A. The GCDB is the Geographic Coordinate Data Base, a geographic grid prepared from land survey and geodetic horizontal control records that graphically portrays the Public Land Survey System. Coordinate data is computed from BLM survey records (cadastral survey plats and field notes), local survey records, and control information to form the GCDB. Control can range from found corners digitized from a USGS quadrangle to Global Positioning System (GPS) placements to published triangulation station locations. The program computes geographic coordinates on a township basis, typically collecting data from townships, sections, section subdivisions, and special surveys such as those of tracts or mineral surveys.

The BLM began collecting the geographic coordinate information in 1989. During GCDB collection, BLM ties official land descriptions to land units delineated by the geographic positions of cadastral survey corners. It is these land descriptions that are used in maintaining land actions like surveys, coal leases, and wilderness designations within the BLM.

A. The web site is located on the Internet at http://www.blm.gov/gcdb.

A. For the initial capability, data are available on the download site for Arizona, Colorado, New Mexico, and Wyoming. Data for Montana will be available soon, with other western states to follow. The download site provides township data in the standard GCDB ArcInfo Coverage format. These coverages are available in ESRI export file format (.e00). Flat files containing line and attribute information will be available for download in the summer of 2000.

A. The new site provides an easy-to-use geospatial selection tool for getting all GCDB data. Data sets that span state lines can also be downloaded at the same time. Users can select a township for download by County, National Forest, BLM field office, BLM 100k-map area, or as an individual township. The download data includes topology (points-geographic coordinates and lines), polygon labels (land descriptions), horizontal control, and regions.