BLM Expands Land Survey Data Access

The Bureau of Land Management has launched a new centralized Land Survey Information Web site that will provide users with geographic information from the agency’s
Geographic Coordinate Data Base (GCDB), part of the Public Land Survey System (PLSS). The new site (http://www.geocommunicator.gov/lsi/) replaces the current BLM
GCDB download site (http://lm0500.blm.gov/).

BLM officials said the new LSI Web site is important, because it provides the public with spatial data that aren’t available anywhere else. Leaders at the agency envision the
easily accessible PLSS data being used as a framework for GIS projects, providing a standard grid format for referencing spatial data. Users can query data by state, principal
meridian, township and section identifiers, allowing them to locate land data based on legal descriptions of the land or geographic coordinates determined using Global
Positioning System receivers.

The geographic coordinates at the LSI site are delivered in ESRI’s open shapefile format and can be viewed graphically using any software capable of reading a shapefile.
The attributes of the shapefile, including the geographic coordinates, are stored in a DBF file and can be viewed in a table in an application such as Microsoft Excel. The
geographic coordinates are available in ASCII format in the GCDB flat file named "township.LX."

Before the new central BLM LSI site went live this spring, users could get data from some of the BLM GCDB state offices, which have served the GCDB flat files from their
Internet sites. The information also was available from a BLM site that served GCDB ArcInfo coverages in the proprietary ESRI e00 file format—not in the current open
shapefiles format. The U.S. Geological Survey is serving PLSS data on its Web site at http://www.nationalatlas.gov, but the atlas data are available only for the township level.

"LSI provides geospatial selection tools that allow the user to select their area of interest quickly and easily," a BLM spokeswoman said. "The old method did not have
geospatial selection tools and required the user to pick the needed townships from a list of township names." Moreover, the GIS coverages were available only at individual
township coverages, meaning users needing regional coverage had to stitch together data using additional GIS tools.

PLSS data aren’t currently available for every state, but BLM officials plan to add data as they become available. The site now covers chiefly states in the west, although
about 300
townships for Arkansas and about 150 townships for Michigan are being added to cover states in the east.

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