A Short Range, High Precision Navigation System for Automated Farming

Robert L. Morris and Ron J. Palmer

Abstract:	This paper presents a design overview and test results of a short range (5000m), high accuracy (30 cm) navigation system developed by Accutrak Systems, Regina, Canada. The primary objective of this system was to provide coordinate information of a sufficient range and accuracy at a price suitable for precision farming. Farm chemical application requires relative positioning accuracy of approximately 15 cm. This represents the vehicle positioning accuracy of an experienced operator. Current chemical applicator guidance systems (colored foam and disc marking systems) provide chemical application accuracy of approximately 60 cm in addition to having inherent disadvantages over an electronic guidance system. The Accutrak Model 2020 navigation system consists of a number of stationary satellite beacons located at a known coordinates and a single mobile beacon. The mobile beacon obtains range measurements to each stationary beacon. In general, a location fix can be triangulated from range measurements to any two beacons. At some positions an accuracy dilution can occur for a beacon pair due to poor geometry between the mobile and the two beacons. Additional beacons remove the effect by providing alternate solutions. A final solution is determined by calculating a weighted average of all beacon pair solutions. The system is currently being used at a number of beta test sites as well as ongoing in-house testing. Initial test results indicate that absolute positioning accuracy is consistently within 30 cm over a 1600 m square with a 4 beacon system. Relative positioning error is less than 10 cm over the same 1600 m square.
Published in:	Proceedings of the 50th Annual Meeting of The Institute of Navigation (1994) June 6 - 8, 1994 Antlers Doubletree Hotel Colorado Springs, CO
Pages:	495 - 500
Cite this article:	Morris, Robert L., Palmer, Ron J., "A Short Range, High Precision Navigation System for Automated Farming," Proceedings of the 50th Annual Meeting of The Institute of Navigation (1994), Colorado Springs, CO, June 1994, pp. 495-500.
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