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Cadastral Survey

Geographic Coordinate Data Base

GCDB Status Map

The Idaho Geographic Coordinate Data Base (GCDB) contains geographic coordinates, and some associated attributes, for most of the Public Land Survey System (PLSS) in Idaho. Coordinates are available for all rectangular corners down to the 1/16 section corner level, and all special survey corners (meanders, mining claims, HES, etc) for those townships that are completely collected. It provides a spatial foundation for the BLM's Automated Land and Mineral Record System (ALMRS) and may be useful to anyone with a requirement to link their data to a spatial PLSS position on the earth's surface.


These coordinates were calculated using the most recent federal survey information available from the PLSS records and using control points from various sources. In some cases, private survey information was also used. The GCDB coordinates represent an approximation of the location of PLSS corners on the earths surface based on the best available evidence input from the record with errors mathematically treated through an adjustment processes. The following two different software packages were used to compute the GCDB: PLSS Coordinate Computation System (PCCS) and GCDB Measurement Management (GMM). PCCS was used first, until May 1993. The file names for the two software packages are different but the contents are essentially the same. 

The PCCS files have coordinates in Latitude/Longitude NAD 27, and Universal Transverse Mercator projection (UTMs - x,y in meters). GMM files have coordinates in all three formats.

Descriptions of most of the files are in the Idaho GCDB Users' Guide. Some files are not listed because they are only used for reworking a township.

To successfully work with the GCDB, you need to know how the point identification system works, the difference between the meaning of reliability in PCCS versus GMM, and some information on control points. These topics are also covered in the Idaho GCDB Users' Guide.

The geographic coordinates and their associated products have NO LEGAL SIGNIFICANCE and should not be used for purposes other than which they were intended such as: restoration of lost corners, establishment of direction, trespass resolution, legal descriptions, etc. which require legal boundary surveys by qualified surveyors. They should also not be used for various other non-cadastral survey purposes like: fencing boundaries, construction, etc.. They could be used for record keeping, mapping, preliminary corner search and planning and other land management purposes.

The initial collection of the raw data for the geographic coordinates and attributes was not done with a requirement for 100% accuracy. In many cases, the only way to resolve conflicting survey records would be to perform an actual on the ground survey. This was not feasible in the initial collection and so some kind of solution was arrived at in order to complete the collection. The GCDB is a dynamic data base which will be continually updated by design, at various times. This may cause problems for some users of GCDB data. Please let us know if you find any problems or can contribute better quality data, either survey theme or control theme. We need your help to improve the quality of our data.

Contact

If you have questions, please feel free to contact Byron McCombs at (208) 373-3992 or email him at bmccombs@blm.gov.