title: Validity and reliability of GPS for measuring distance travelled in field-based team sports.
abstract: The aim of the present study was to examine the effects of movement intensity and path linearity on global positioning system (GPS) distance validity and reliability. One participant wore eight 1-Hz GPS receivers while walking, jogging, running, and sprinting over linear and non-linear 200-m courses. Five trials were performed at each intensity of movement on each 200-m course. One receiver was excluded from analysis due to errors during data collection. The results from seven GPS receivers showed the mean (± s) and percent bias of the GPS distance values on the 200-m linear course were 205.8 ± 2.4 m (2.8%), 201.8 ± 2.8 m (0.8%), 203.1 ± 2.2 m (1.5%), and 205.2 ± 4 m (2.5%) for the walk, jog, run, and sprint trial respectively. Walk and sprint distances were significantly different from jogging and running distances (P < 0.05). The GPS distance values on the 200-m non-linear course were 198.9 ± 3.5 m (-0.5%), 188.3 ± 2 m (-5.8%), 184.6 ± 2.9 m (-7.7%), and 180.4 ± 5.7 m (-9.8%) for the walk, jog, run, and sprint trial respectively; these were significantly lower than those for the corresponding values on the linear course (P < 0.05). Differences between all non-linear movement intensities were significant (P < 0.05). The overall coefficient of variation within and between receivers was 2.6% and 2.8% respectively. Path linearity and movement intensity appear to affect GPS distance accuracy via inherent positioning errors, update rate, and conditions of use; reliability decreases with movement intensity.
authors.affiliation: School of Human Movement Studies, The University of Queensland, St. Lucia, Queensland, Australia. adriangray@uq.edu.au
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Gray
authors.forename: David
authors.initials: D
authors.lastname: Jenkins
authors.forename: Mark H
authors.initials: MH
authors.lastname: Andrews
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Taaffe
authors.forename: Megan L
authors.initials: ML
authors.lastname: Glover
mesh_terms: D000328:Adult; D054874:Athletic Performance; D040362:Geographic Information Systems; D006801:Humans; D007590:Jogging; D008297:Male; D009068:Movement; D015203:Reproducibility of Results; D012420:Running; D013177:Sports; D016138:Walking