Mapping property boundaries in Cook County has a long and varied history. Years ago, boundaries were hand-drawn on a series of paper maps with little context. More recently the first digital representations were captured using drafting software and stored as separate computer drawing files.
Today these boundaries are managed as a continuous countywide fabric in the county’s Geographic Information System (GIS). With GIS the data can be displayed with other map layers and used for a variety of spatial analysis. Despite these advances the accuracy of these boundaries has always been a bit of a question.
In today’s high-tech world with GPS technology and aerial imagery it’s easy to assume lines on a map are true representations of real boundaries, but that’s not always the case.
To gain a better understanding of the accuracy of mapped property boundaries, Cook County is working to compile an inventory of the corner positions that control these and other important boundaries.
An often misunderstood or forgotten part of land records information is the very framework that defines land ownership throughout most of our country, the Public Land Survey System (PLSS).
The PLSS is the legal framework that divides land into townships, sections, and smaller fractional units for locating and describing land ownership and property rights. Every property deed filed in the County Recorder’s Office includes a legal land description connecting it to this system of rectangular surveys.
While these boundary lines aren’t visible on the landscape the corner positions marking their beginning and ending points often are. Beginning in 1859 federal survey crews set out to establish the original PLSS corner monuments in Cook County.
Today, we rely on licensed land surveyors to keep these critical corner positions in check. These corner monuments are the physical evidence that determine PLSS boundary lines and are the subject of a new collaborative county mapping project.
Staff from the Recorder’s Office and the GIS division of the MIS department are excited about teaming up with county contract surveyor Wayne Hensche to bring high quality PLSS data to all map users.
Hensche is currently compiling high accuracy coordinate data that will be used to locate these critical corners in the county’s GIS and mapping applications. This new corner data will allow the county to adjust PLSS boundary layers to known positions and better represent property boundaries on maps. It can be very confusing and frustrating when property lines drawn on a map don’t line up with the underlying landscape when viewed over aerial imagery.
It’s also challenging and time-consuming to understand the relationship between mapped property boundaries and the improvements inside them such as buildings, roads, wells, septic systems, trails, etc. This project will help us start to make adjustments in a controlled and meaningful way, moving us to a more accurate system of land records.
It’s important to note that this project will require a phased approach to make data improvements across the county over time.
The current scope targets populated areas running parallel to Lake Superior with a completion goal set for this coming fall. Continued work will expand inland and up the Gunflint Trail corridor to eventually capture controlling corner data for most areas of private ownership in the county.
Additionally, this project will include a web mapping application for users to explore all the information we’re gathering about the PLSS framework and the corner points that control it. This will be an especially useful service to the survey community. Land surveyors require detailed information about PLSS corners to perform a survey.
Because all land ownership is tied to the PLSS framework and its controlling corners, access to quality corner information sources is where it all starts. When a surveyor reviews a legal land description they need to locate the corner that connects it to the PLSS framework before any pins can be set in the ground. By bringing together as much as we can of the available survey evidence for PLSS corners in one simple to use, easily accessible mapping application, we hope to save surveyors time. With fewer hours spent researching corner records, land surveys should take less time and cost the private landowner less.
Stay tuned for further updates as this exciting project progresses.
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