Reliability and Accuracy of 10 Hz GPS Devices for Short-Distance Exercise.

The use of GPS technology for training and research purposes requires a study of the reliability, validity and accuracy of the data generated (Petersen et al., 2009). To date, studies have focused on devices with a logging rate of 1, although it seems that more frequent sampling can increase the accuracy of the information provided by these devices However, we are unaware of any study of the reliability and accuracy of GPS devices using a sampling frequency of 10 Hz. Thus, the aim of the present research was to determine the reliability and accuracy of GPS devices operating at a sampling frequency of 10 Hz, in relation here to sprints of 15 m and 30 m and using both video and photoelectric cells. Nine trained male athletes participated in the study. Each participant completed 7 and 6 linear runs of 15 m and 30 m, respectively (n = 117), with only one GPS device being used per participant. Each repetition required them to complete the route as quickly as possible, with 1 min recovery between sets. Distance was monitored through the use of GPS devices (MinimaxX v4.0, Catapult Innovations, Melbourne, Australia) operating at the above mentioned sampling frequency of 10 Hz. In addition , all tests were filmed with a video camera operating at a sampling frequency of 25 frames. Data were collected during what were considered to be good GPS conditions in terms of the weather and satellite conditions (number of satellites = 10.0 ± 0.2 and 10.3 ± 0.4 for sprints of 15 m and 30 m, respectively). Distance was measured using a tape measure. Electronic timing gates (TAG-Heuer, CP 520 Training model, Switzerland) were used to obtain a criterion sprint time accurate to 0.01 s, with gates being placed at the beginning and end of the route (Petersen et al., 2009). Logan Plus v.4.0 software was used to synchronize the GPS files with the video, establishing the beginning of action when the participant crossed the initial photocell; this was then added to the duration obtained through the photoelectric cells. The accuracy of data within and between devices is shown in Table 1. The average values are close to those established in tests of 15 m and 30 m, with errors getting smaller when the devices were used over 30 m. The intra-device reliability is depicted in Figure 1, showing greater stability over 30 m than 15 m. …