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Tracking Biosolids with Satellites
by David Smith, UNL Extension Assistant
What is GPS?
GPS (Global Positioning System) is a system of radio-navigation satellites set up by the Department of Defense for location on the earth's surface. Satellites that orbit the earth are constantly sending information about their position back to the earth's surface. These signals can be picked up by GPS receivers and then used to determine the location of the receiver in terms of known earth locations or coordinates. For instance, a person wants to determine the location of a stop sign at a certain intersection. The person would set up the receiver at the stop sign and gather enough satellite positions for the receiver to determine its position and therefore the position, or coordinates, of the stop sign. GPS is mobile, quick and efficient, and would allow for a large number of locations(e.g. stop signs) to be taken in a day, as opposed to a survey crew or a more traditional method of determining locations. These GPS locations can then be used to map features, or incorporated into a GIS for database construction or further analysis.
Accuracy: The accuracy of the positions recorded by the receivers is dependent on a number of factors. Satellites must be "seen" by the receiver for accurate readings, so the number of satellites in the horizon viewable by the receiver is a factor in accuracy. Trees, buildings and other structures may obstruct the signals the GPS unit can receive, and degrade the accuracy of positions. In addition, the unit itself will have an influence on the accuracy of positions. Some more inexpensive units only give accuracies within hundreds of meters of the true earth location, while with more expensive units, millimeter accuracy is attainable.
Uses in The Biosolids Program
The use of GPS is rapidly expanding. From navigation to surveying and precision farming, the possibilities of using GPS in a geographic application are extensive. Lincoln's Biosolids Program has embraced this technology for the mapping of geographic features such as fields, storage sites, and soil sampling locations. Historically in this program, the outlining of fields for application was done by hand, usually by the cooperator. The use of GPS offers a consistent and highly accurate way of documenting fields, and the storage sites and soil test sites that have previously not been mapped. The features that are important for the program can be easily determined by GPS, and a database of records for all those features, with consistent standards is a major benefit for the program. Finally, the GPS data is easily incorporated into the Biosolids GIS for analysis of the fields for potential conflicts with regulations and other analytical activities.
We use a Trimble Pathfinder Pro XR GPS receiver - photo right (http://www.trimble.com/) for the recording and mapping of features and Pathfinder Office software for the processing of the GPS data.
PHOTO Credit: Vicki Jedlicka
Lincoln's biosolids recycling program is a joint collaboration between the City of Lincoln, Public Works and Utilities Department and University of Nebraska-Lincoln Extension in Lancaster County with assistance from the University of Nebraska Agronomy Department, Lincoln/Lancaster County Health Department and the Natural Resources Conservation Service.
University of Nebraska-Lincoln in Lancaster County
Barb Ogg or David Smith
Web site: lancaster.unl.edu
444 Cherrycreek Road, Suite A, Lincoln, NE 68528 | 402-441-7180
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