|By Timothy Kennedy|
|June 23, 2011|
Coordinates of PLSS corners
Mapping coordinates can be determined for a PLSS corner. Since the range of accuracy in coordinate values can be large, users of the information need to understand clearly how the values were produced in order to avoid misuse. Search for metadata, and contact the producer if questions remain.
The highest accuracy PLSS-corner coordinate values are typically a result of work using "survey-grade" GPS receivers. Contact the County Surveyor or County Land Information Office. (Prior to the 1990's much of this work would have been done through traditional traverse work).
Less robust GPS equipment (e.g., "resource-grade") can deliver approximate values, as can a process called analytical aerotriangulation which relies on the location of a ground object being visible on aerial photographs. Once the aerotriangulation is done for a small number of points in an area, somewhat lower-accuracy coordinate values can then more quickly be determined for additional points (e.g., section corners marked on the ground prior to the photography acquisition) through photogrammetric methods.
Low-accuracy coordinate values can be derived from maps such as the USGS topo maps. A statewide digital version of these points has been compiled from the 1:24,000-scale map series into a GIS data layer called the LandNet which includes not only PLSS section corners and lines but further has been mathematically subdivided down to nominal 1/4 section polygons (nominally 40 acres each). Analysis by several county surveyors has found that LandNet coordinates are typically within 50 feet of their true positions. This level of accuracy meets standards for the USGS top maps.
Another base map that might be used to derive PLSS corner coordinates is a digital orthophoto. Here, visual clues to the corner location are critical, and the inherent accuracy level of the orthophoto must also be taken into account.
Status of remonumentation (WLIB survey)
Remonumentation of PLSS corners is an ongoing project across the state although a number of counties have completed this work. An annual survey of land information modernization provides an overview of remonumentation status by county.
Original survey records and maps
The PLSS was put in place on the land by the federal government's General Land Office (GLO). Surveyor's hired by the GLO were required to record their work in notebooks of which only a few copies were made. These historical documents are maintained by the state's Board of Commissioners of Public Lands (BCPL) and by the Wisconsin State Historical Society (SHS). (The GLO was later absorbed into the modern agency called the Bureau of Land Management (BLM) which today manages large areas of land in the western states, retains mineral rights to some lands in Wisconsin, and is the custodian of the "patents" which are the legal documents indicating conveyance of ownership from the Federal Government to the first private owner).
GLO Field notebooks
The notebook pages have been available as microfilm from the SHS and copies of these are known to exist in some county surveyor' offices. A recent project involving BCPL has resulted in the digital scanning of all of the notebook pages. These scanned images are available over the Internet through a site developed by the University of Wisconsin-Madison's General Library System.
GLO Plat maps
Shortly after the field surveys were completed in an area, the notebook contents were used by GLO staff in Chicago to draft plat maps showing the layout of the PLSS in context of noted geographical features such as rivers, lakes, trails, and settlements. These maps have been scanned by the BCPL and made available, one CD-ROM per county. These digital image files may be linked into the web-based notebook contents project described immediately above.
Records at National Archives office in Chicago
During the 1930's, the Civilian Conservation Corps (CCC) did some field work in support of finding and/or marking of PLSS corners. These projects were primarily in northern forested areas, and the first place to search for records of this work is at the county courthouse. The State Archivist at the Wisconsin State Historical Society is a seconary source and can assist with searches of the National Archives.
Finding modern PLSS monuments in the field
Who to ask for advice; trespass issues
Professionals are the best source for assistance in locating PLSS monuments. Land surveyors work in private practice and many counties and cities have a staff surveyor. Each county has a land information office. Be aware that in reaching the location of some monuments you may be trespassing on private land.
If you become aware of a PLSS monument that has been disturbed, report this immediately to the county (surveyor or land information office) or municipality (surveyor or engineer). Do not attempt to "repair" or "restore" any such damage as you may actually make matters worse.