The Land Survey Information System database represents the Public Land Survey System (PLSS) GIS layer and is based on official land surveys of the United States.
Detailed FGDC compliant metadata is delivered with the GCDB GIS data. Data contact information, the data source, and item descriptions are included in the metadata.
Projection Information:
Datum: NAD83
The geographic transformation method used to convert the GCDB data from the NAD27 datum to NAD83 datum was "GCS_NAD_27 to GCS_NAD_83_NADCON".
The PLSS shapefiles are now coming from the National Integrated Land System (NILS) andare in NAD83 datum. The PLSS shapefiles available from LSIS before May of 2004 were in NAD27 datum. Alternate source data has been converted to NAD83 as well. The same file format has been maintained for backward compatibility reasons, except as noted below. Review the Metadata for column descriptions. The geographic transformation method used to convert the GCDB data from the NAD27 datum to NAD83 datum was "GCS_NAD_27 to GCS_NAD_83_NADCON".
| Twnshp | ||
| * | Added attributes: datemodifi, and label | |
| * | Removed obsolete/unused attributes: townid, plssid, and twnmet | |
| First | ||
| * | Added attributes: sectionkey | |
| * | Removed obsolete/unused attributes: sectid, townid, frsttp | |
| Ladesc | ||
| * | Added attributes: minorsub, sectionkey, secfrt, sectn, secdup, qsection, ,qqsection (note-the qsection is now only storing the quarter section and the new field qqsection stores the quarter-quarter section) | |
| * | Removed obsolete/unused attributes: legid, geoid, laagnt, laindx, latype, ladate, qsectn, surorg | |
| Recbnd | ||
| * | Added attributes: | |
| * | Removed obsolete/unused attributes: recbid, lineid, bounds, legsts, cmmnt | |
| Coords | ||
| * | Added attributes: ptunique | |
| * | Removed obsolete/unused attributes: cvalid, pntnm, adjid, north, east, zacc, hdatum, vdatum, crdsys, prjunt, avgrel, maxrel | |
| Coordmeas | ||
| * | Added attributes: ptunique | |
| * | Removed obsolete/unused attributes: pntnm, north, east, srcid, capmet, statnm, statidp, valstat, uscflg, cmeasid | |
Projection: Geographic Coordinates
Unit of Measurement: Decimal Degrees
The BLM began collection of the geographic coordinate information in 1989 and the data collection effort continues today. GCDB data has been collected for approximately three quarters of the townships in the Western United States. The BLM Eastern States Office has collected GCDB over 400 townships east of the Mississippi River.
BLM collects the GCDB data on a township basis. The survey boundaries are delineated by determining geographic coordinates for established survey positions. GCDB specialists use weighted least squares adjustments to determine the best position for corners of townships, sections, aliquot parts, government lots, and special surveys. Next, official land descriptions are assigned to each land unit. The records are then reformatted so Geographic Information System (GIS) software can be used to view the PLSS information spatially. The data is imported to the National Integrated Land System geodatabase and then served to the public through the GeoCommunicator website.
GIS data from alternate sources is also available.
The LSIS township index can be viewed on the Internet, along with U.S. highways and Federal administrative and mapping boundaries. These layers can be turned on and off to help the user locate an area of interest.
ESRI's ArcIMS (Internet Mapping Service) software is being used to distribute the PLSS. Geospatial selection tools provide the user with the capability to download GIS shapefiles for the area they are interested in. Counties and Federal administrative areas are pre-packaged for easy selection and quick download. Once the GIS data is downloaded to the desktop, it can be viewed or incorporated into a local GIS.
The LSIS website supports viewing the township lines that comprise the LSIS township index. The GCDB shapefiles that are downloaded include survey lines to the section level and below. This latest version of LSIS also supports viewing the actual data, so all of the detail represented in the GCDB and alternate sources, is viewable on the desktop using the LSIS source image service. This capability allows GIS tools such as ArcExplorer and ArcGIS to be used to view or "stream" the data online.
For help in using the system, use the "How to Access the Land Survey Information System" Guide or our online help system. For more information on the National Integrated Land System (NILS), please visits our NILS Website.
For information on GIS shapefile format, go to http://www.blm.gov/wo/st/en/prog/more/gcdb/blm_gcdb_standards.html
For information on the GCDB project, contacts and standards visit the project Web site at http://www.blm.gov/wo/st/en/prog/more/gcdb.html.
For information on the National Integrated Land System (NILS) project, visit the NILS project Web site at http://www.blm.gov/wo/st/en/prog/more/nils.html.