Geographic Coordinate Data Base
BLM is building an automated Land Information System(LIS) for improved public land management. BLM will use the LIS in making resource management decisions such as processing applications for mineral leases, designating utility corridors, issuing land use permits, locating wildlife habitat improvements, preparing timber sales, evaluating alternatives in environmental assessments and land use plans, and generating reports and maps.
BLM is automating fundamental types of information for its Land Information System: The Geographic Coordinate Data Base from the National Public Land Survey System; land and mineral records; natural resource data files; and base maps. Thus, the Land Information System will for the first time tie BLM's records and natural resource data to legal descriptions of specific land parcels through a unified automated system.
Fundamental to this approach is the use of a common reference system for the different types of data - a Geographic Coordinate Data Base built from the Public Land Survey System. The collection, analysis, and management of the data is the responsibility of the Branch of Cadastral Survey. The diagram shown above indicates current progress in the data collection.
Accurate locations for monuments within a township can be obtained by using a variety of control survey techniques such as a global positioning system. Other sources of coordinates may also be used to supplement the data base such as digitizing the location of found corners from various map sources or photographs. These locations can be used with the bearings and distances of the surveys to calculate latitude and longitude of the remaining corners. These geographic coordinates may better represent the location of monuments on the ground than the early cadastral plats. Using the concept of an automated Public Land Survey System/Geographic Coordinate Data Base (PLSS/GCDB), survey information that is now manually drawn on maps from seperate documents can be shared by computer and displayed automatically on one map, with the legal parcel corner as the foundation to which all other information is registered or aligned.
The PLSS/GCDB will eventually contain coordinates for corners of rectangular and special surveys including metes and bounds. As geographic coordinates are established for resource boundaries, resource data can be merged with the most current ownership, status, and survey data because all of the necessary informaton is located in the same latitude and longitude or compatible reference system.
GCDB User's Guide
"The GCDB Users' Guide explains the processes used to collect the data. It explains the GCDB township naming conventions and point identification system. In addition there are examples of what some of the files contain that are created during collection. Not all files created are included, some are meaningless to the user. These files are used for analysis of the data during processing. The files that are included in this guide contain the data that most users will be interested in. Also included, is the GMM glossary of terms."
Download GCDB Data
The latest Geographic Coordinate files can be downloaded from the “BLM Secure File Transfer Site” (Link to www.blm.gov/sfta).
Follow the directions to log onto the site. The data files for specific townships are located within the meridian directories at the following path: Pub/CA/gcdb
This data is updated frequently, so keep checking back for current information. Note: No warranty is made by the BLM for use of the data for purposes not intended by BLM.
Questions concerning this program can be directed to Dave Grainger.