Consumer-grade global positioning system (GPS) accuracy and reliability

Our primary study objective was to test the accuracy and reliability of consumer-grade GPS receivers in a variety of landscape settings. We established three measurement testing courses in open sky, young forest, and closed canopy settings within a conifer-dominated forest in western Oregon and rigorously tested the positional accuracy of six different GPS. All units were produced by established GPS manufacturers. We found that performance varied, in some cases considerably, among units and appeared to be influenced by. canopy (over and satellite availability. Among the top GPS performers, we determined that users could expect positional accuracies within approximately 5 m of true position in open sky settings, 7 m in young forest conditions, and 10 m under closed canopies.