Vol 4; Issue 2: Straight to the Point
One question that people often have for land surveyors is; where do the coordinates that you are assigning to a point on the ground come from? The most accurate answer to this question would involve a lengthy and technical course that most people would not care to endure. How can a grid system be so complicated? In order to begin to understand the concept it is important to think of the big picture.
The earth is round. Imagine trying to wrap a large piece of grid paper around a basketball. As you may be able to picture in your head, you are going to have wrinkles, overlaps and perhaps even tears of your grid. From point A to point B may be an entirely different length and direction then it would be when your grid paper was laying on a flat surface. This will not work. Now imagine taking a smaller piece of grid paper and covering only a couple square inches of the ball. The paper remains flatter and your grid less distorted. This is the basic concept of why so many different coordinate systems exist. In reality, the more localized the area, the less distortion caused by the shape of the earth.
In the United States we have what is called State Plane coordinate system. This system gives each state, usually multiple zones in each state, its own coordinate system based on the map projection that makes the most sense. In Minnesota, we have taken the idea a step further.
The Minnesota County Coordinate System gives each individual county (some have multiple zones) its own coordinate system based on the map projection that makes the most sense for each county. This system is credited to University of Minnesota Professor Gerald Johnson and was published and maintained by the Minnesota Department of Transportation. The success of the Minnesota County Coordinate System has not gone unnoticed. Other states have modeled and will continue to model similar county coordinate systems after Minnesota.
Matt Arnold, LSIT
Posted on Fri, November 6, 2015
by Kellie Dixon