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Dynamic Testing of GPS Receivers

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  031013,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.15385)
Authors:   Randal K. Taylor, Mark D. Schrock, John Bloomfield, Ganesh Bora, Gary Brockmeier, Wally Burton, Brandon Carlson, Joshua Gattis, Ross Groening, Jim Kopriva, Nathan Oleen, Jessica Ney, Chad Simmelink, a
Keywords:   GPS Accuracy, standards, vehicle guidance

The popularity of GPS-based guidance systems for agriculture is increasing. However, no dynamic test standards are available to evaluate these receivers. In April 2002, GPS receivers were dynamically tested on a 0.8 km length of railroad track using a small rail cart. The track was surveyed with an RTK GPS receiver and referenced to a NGS benchmark. The GPS receivers were evaluated over a 24-hr period. The tests were conducted in both directions and at 2 different speeds. Cross-track and pass-to-pass errors were determined for a John Deere StarFire receiver with a dual frequency correction and a Trimble AgGPS132 in the autonomous mode. Cross-track errors were sequentially correlated creating problems for using typical statistical analysis methods. A Voronoi step interpolation method was used to generate evenly spaced data for Fourier analysis. Fourier analysis indicated that the cross-track errors contained significant periodic structure below 4 cycles per day. This implies that cross-track accuracy tests should be conducted for a minimum of 12-hr durations. Fourier analysis indicated that pass-to-pass errors were more random than cross-track errors, with no clear concentrations of frequency content, implying that pass-to-pass accuracy tests can yield meaningful results in less time than required for cross-track accuracy testing.