Validity and Reliability Comparison of GPS and LPS

To show potential progress, and in particular, to determine whether a true sampling rate above 10 Hz further improves the validity and reliability of the GPS [12 (link)], recently released 18 Hz devices (EXELIO srl, GPEXE PRO, version M03, Udine, Italy) [31 ] were evaluated together with established 10 Hz devices (Catapult Innovations, MinimaxX S4, version 6.71, Melbourne, Australia) [32 ]. While the exact sampling rate of the recently released GPS devices is 18.18 Hz, we rounded the sampling rate to 18 Hz for allowing a more fluid reading. The 10 Hz devices were chosen as a representative GPS standard because these devices are frequently used in team sport practice and applied studies [33 (link)] and in numerous previous validation studies [12 (link)], which collectively showed that these devices currently allow the most valid and reliable GPS assessment of team sport specific measures [12 (link)]. In accordance with previous studies [10 (link), 34 (link)], all GPS devices were activated 15 min prior to the data collection to allow for satellite lock, and the signal quality was determined via both the number of connected satellites and horizontal dilution of precision [16 (link)]. Both GPS technologies measured the instantaneous velocity via the Doppler-shift (i.e., from the changes in the time signals emitted by the satellites) [16 (link)] as reported by the manufactures [31 , 32 ].
To compare the validity and reliability between LPS and GPS technologies [6 (link)], one recently released LPS (KINEXON Precision Technologies, KINEXON ONE, version 1.0, Munich, Germany) [35 ] was selected. This LPS was chosen because it operates at 20 Hz and allows (from this technical aspect) a comparison with the latest GPS using a similar sampling rate. The LPS was installed, calibrated, and checked for its accuracy by one technician from the manufacturer. Four meters around the circuit, 12 antennae and one base station were positioned at four meters above the ground. The devices worn by the athletes transmitted time signals via radio-technology to the antennae, which sent the signals forward via a wide local area network (WLAN) to the base station. Using all of the signals, the base station then calculated the actual x,y position of the devices within the circuit [35 ]. Subsequently, instantaneous velocities were computed by positional differentiation (i.e., distance over time, whereas the distance was obtained from the changes in the x,y positions within each signal) [16 (link)]. According to previous LPS studies [4 (link), 8 (link)] and for simulating the data traffic, for example, of two soccer teams, 20 devices randomly placed on the ground within the circuit were additionally activated during the data collection. The setup of the LPS is also shown in Fig 1.