## 1 Introduction  
The use of wearable devices for quantifying and monitoring exercise is a basic concern when designing exercise physiology and sport performance studies [1]. In contemporary competitive sports, positional tracking systems are currently used to perform time-motion and tactical analyses [1]. These different systems can be categorized according to the type of technology employed. These technologies include wearable radiofrequency systems, such as global navigation satellite systems (GNSS) [2, 3], local positioning systems (LPS) [4, 5], ultra-wide-band systems (UWB) [6, 7] and optical tracking systems, such as multiple camera video-based computerized tracking [3, 8]. Each class of system has specific advantages and disadvantages [3, 9, 10]. The accuracy of each system is one distinguishing characteristic. At present, tracking systems are mainly used for time-motion analyses (e.g., distance covered, running speed), which provide important information for the assessment of external loads [11]. For such applications, all systems have sufficient accuracy [4; 12; 13]. GNSS has been the most studied system. Overall, it has been proven to be a valid and reliable instrument for distance and speed profile measurements during typical team sports actions [14], although, in short actions of high intensity and with changes of direction, limitations of accuracy have been reported [14]. In addition, some additional considerations should be taken into account, such as the sampling frequency of the devices, the quality of the satellite connection or the horizontal dilution of precision (see more in [PERSON] et al. [15]). UWB-based tracking systems have been proven to be accurate systems for distance and speed measurements [6; 7; 12]. Even so, a previous study established that GPS and UWB are similar (not significant difference between them) in accuracy and inter-unit reliability for time-motion analysis [12]. The majority of these studies have assessed the accuracy of distance covered and speed using predefined test courses and time gates as references [4; 16; 17]. A different method should be used to evaluate the accuracy of the position of players on the court or to estimate instantaneous velocities (real-time analysis). Only three studies have evaluated position data, and these studies used LPS-based technology with video analysis as a reference [5; 18; 19]. LPS and video analysis are costly and complex to use. In particular, the reference system is based on fixed cameras and can therefore only acquire data in restricted areas [20]. In this sense, no studies have been found that have evaluated the accuracy of a tracking system in a complete field of play, where instead they only exist in confined and controlled spaces [3; 5; 18; 19; 21]. The capture volume is dependent on the maximum number of cameras and the field of view of each camera. A high number of cameras results in significant practical difficulties regarding cost, portability, calibration, synchronization, labor and set-up [22]. For this reason, the present study developed an alternative accuracy assessment method that does not require any instrument other than a device with software including a GIS (geographic information system) application. Moreover, UWB technology is the ideal radio frequency-based candidate to provide positioning information in any environment (indoor and outdoor) [23], but especially for indoor conditions, where GPS cannot operate, and others radiofrequency systems have problems in accuracy (e.g., interference with the radio frequency signal) because of the different architecture and buildings used for different courts. These differences refer to the elements and their arrangement, such as distance from the court to the walls, marker position, etc. Therefore, the accuracy of the system can change, and each system should be evaluated in the court where it will be used. For this purpose, a different and easy low-cost assessment of position data accuracy was developed.