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ARS Home » Research » Publications at this Location » Publication #72057
Title: LINEAR MOVE IRRIGATION SYSTEM POSITION AS DETERMINED WITH NONDIFFERENTIAL ECONOMIC GPS UNIT

Author
item HEERMANN, DALE - USDA ARS NPA
item BUCHLEITER, GERALD - USDA ARS NPA

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Other
Publication Acceptance Date: 6/11/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: A four span linear irrigation system is being equipped with eight segments that can be controlled individually for variable application of water. The control is accomplished by pulsing the individual segments to obtain the desired treatment. Equally important to the control along the lateral is the control in the direction of travel. A position sensor on the system is required for controlling the application appropriately in the direction of travel. The use of economical GPS units is investigated. The use of typical GPS differential technology would provide acceptable accuracy but would be quite expensive for commercial application of the variable rate sprinkler system. Experimental data collected with the economical GPS unit has shown that normal operation would result with a range in error of 30 meters. This is unacceptable for controlling variable rate application. The data was analyzed by calculating 30 minute running averages and it was found that the running average had a range of error equal to 3 meters. Th running time of each tower can be obtained easily from the linear move system. This running time when multiplied by a speed of the tower provides an estimate of the speed. The major problem with this estimate is the change in speed due to a differential slip and thus a change in speed. An algorithm has been determined that uses the 30 minute average of the GPS data to adjust the speed during operation. With this algorithm the expected error is reduced to 1 meter which is assumed to be adequate for controlling the variable rate application in the direction of travel. The changes from one rate to another are not instantaneous since the overlap and spray distance of individual sprinklers are about 3 meters.