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Land Surveyor: GPS – What it Can and Cannot Do

Site Sketch - 2Land surveyors use a detailed technique of determining the air, land, and water boundaries of a particular piece of land. In most instances, land surveying is performed for the purpose of developing land maps or determining property boundaries for personal and official use.

As recently as the 1990s, the measurements that were needed to complete a land survey were determined by using basic, rudimentary equipment, such as electronic distance measurement (EDM), tape measures, and theodolites. Combined with the use of physics, mathematics, and engineering, these basic measurements were used to determine the boundaries of a particular tract of land. The most common mathematical techniques that were used by surveyors include triangulation and trilateration.

As with many industries, the work of land surveyors has been transformed by the introduction of new technology. One of the most dramatic changes to land surveying has come from the introduction of a global positioning system, or GPS. GPS devices make surveying land – especially vast pieces of land – much faster and more accurate. Although many land surveyors utilize GPS technology to create more accurate surveys, there are still some surveyors, especially in rural areas like Northern Michigan that still rely exclusively on older techniques. This disparity in the sophistication of the surveying tools can widen the gap between different surveyors. To increase the odds that your survey will stand undisputed find a Northern Michigan surveyor that uses GPS.

GPS land surveys are made based on trilateration. Trilateration is used to determine the positioning of certain objects through the use of geometry. In terms of land surveying, these objects are landmarks or boundaries of a particular tract of land. This particular form of trilateration is performed solely by satellites, which orbit the Earth.  In general, GPS measurements are incredibly accurate. When used correctly, GPS components can pinpoint important locations and measurements within millimeters of accuracy.

Though GPS measurements are considered to be highly accurate and dependable, they are not without error. As with any type of machinery, the tool is only as accurate as the person using it. This is why GPS is often used in conjunction with other traditional, human-controlled land survey measurements. Some of the most common GPS issues include:

  • The degree of human error that is present. If the operator reads an instrument incorrectly or makes an inaccurate judgment, the information as provided by the GPS and interpreted by the user will be incorrect.
  • Environmental conditions can affect GPS measurements. The presence of tree cover, buildings, electric lines, and even temperature variations can cause incorrect GPS measurements.
  • The inclusion of resolution limits. As with any measurement, GPS measurements are not exact. They include a marginal degree of error. In most instances this error is miniscule – an average of 20 mm horizontally and 30-40 mm vertically are the average degrees of error for GPS measurements when conducting land surveys. Regardless of how small, it is important that the surveyor be aware of these limitations.

David G. Heydlauff, PS is the owner of DPS Surveying and Mapping and a Northern Michigan land surveyor located in Traverse City, Michigan.  DPS Surveying and Mapping provides surveys, mapping and legal expert services to the Northern Michigan area including, Antrim, Benzie, Grand Traverse, Kalkaska, Leelanau and Manistee.