Roland Leser

Accuracy of the LPM tracking system considering dynamic position changes

Abstract This study investigates the accuracy of the tracking system LPM (Local Position Measurement). The goal was to determine detailed error values of the system in the context of sports performance analyses. Six moderately trained male soccer players (amateur level) performed 276 runs on three different courses at six different speeds. Additionally, ten small-sided game plays were carried out. All runs and game plays were recorded with the LPM tracking system and the motion capture system VICON simultaneously. VICON served as the reference system. The absolute error of all LPM position estimations was on average 23.4±20.7 cm. The estimation for average velocities varied between 0.01 km h−1 and 0.23 km h−1, the maximum speed estimations differed by up to 2.71 km h−1. In addition, the results showed that the accuracy of the LPM system is highly dependent on the instantaneous dynamics of the player and decreases in the margins of the observation field. These dependencies were quantified. Considering commonly used applications of position tracking systems in sports (Leser, Ogris, & Baca, 2011), the accuracy of LPM is acceptable for position and velocity estimations. The system provides valuable results for average velocities but seems to be far less reliable when dealing with high dynamic movements and measuring instantaneous velocities.

Local Positioning Systems in (Game) Sports

Position data of players and athletes are widely used in sports performance analysis for measuring the amounts of physical activities as well as for tactical assessments in game sports. However, positioning sensing systems are applied in sports as tools to gain objective information of sports behavior rather than as components of intelligent spaces (IS). The paper outlines the idea of IS for the sports context with special focus to game sports and how intelligent sports feedback systems can benefit from IS. Henceforth, the most common location sensing techniques used in sports and their practical application are reviewed, as location is among the most important enabling techniques for IS. Furthermore, the article exemplifies the idea of IS in sports on two applications.

Accuracy of an UWB-based position tracking system used for time-motion analyses in game sports

Abstract The main aim of this study was to determine the accuracy of the ultra-wideband (UWB)-based positioning system Ubisense, which is used for time-motion analysis in sports. Furthermore, some alternatives for positioning the systems transponders on the atheletes, as well as the accuracy depending on the location of measurement, were tested. Therefore, in a pre-study, some basic issues were examined (measurement assumptions and consistency and location of the systems transponder used for position detection), and position measurements at the borders and in the centre of a basketball field were performed. In the main study, 13 male basketball players (15.8 years ± 0.6; 187.9 height ± 3.4; 77.5 weight ± 3.7), equipped with a Ubisense transponder mounted on top of their heads, handled a trundle wheel during simulated match play. The players with the trundle wheel participated passively in the match by following one of the ten competing players. The distance measurements of the trundle wheel were used as reference values and compared to the Ubisense distance estimations. Best results were found with the measurements of a single mounted transponder on top of the athletes heads. No differences were detectable in the accuracy between measurements in the centre and at the borders of the basketball field. The (Ubisense) systems difference to the (trundle wheel) reference was 3.45 ± 1.99%, resulting in 95% limits of agreement of −0.46–7.35%. The study indicates the examined systems sufficient accuracy for time-motion analysis in basketball.

Expert-oriented modelling of a 1vs1-situation in football

The aim of this study was to create a suitable model for analysing tactical behaviour in one versus one (1vs1) situations in association football. First, expert interviews were used to extract expert knowledge, in order to define an adequate kinematic testing model. Second, youth football players were examined via this model, and the data collected was used to check the suitability of the testing scheme. The performance of the players participating in 75 1vs1 trials was recorded via the LPM® (Local Positioning Measurement) system. In this context, another aim was to develop a concept to automate 1vs1 performance analysis. The test setting chosen consists of a frontal form of 1vs1 confrontations, where one striker is in control of the ball and trying to overcome a defender, in order to create a goal scoring opportunity. One trial is divided into four key moments and three phases, at which different kinematic parameters (i.e., positions, velocity and acceleration) of the competing players are collected. The evaluation of the available data indicates that the attacker’s as well as the defender’s accelerations at the moment when the striker tries to pass the defender are key features to perform successfully in 1vs1 situations.

A comparison between the structure in elite tennis and kids tennis on scaled courts (Tennis 10s)

This study aimed to compare the playing structure between ATP tennis and three different kids age groups following the ITF’s “Tennis 10s” concept. The playing structure was defined by means of 17 conventional performance parameters. All in all 48 matches were analysed by proper video footage. Sixty-seven different players participated in the study. The ATP group comprised a mixture of different player types (offensive/defensive base line players, serve and volley players etc.) competing in the round of 16 matches up to finals in official ATP tournaments. The kids sample consisted of the best 20 Austrian players from the age groups Boys Under 9 (U9), Under 10 (U10) and Under 12 (U12). Absolute and relative differences as well as one-way ANOVA were calculated between the groups. The study’s results indicate that the playing structure of the U9 is most similar to ATP tennis among all youth groups, followed by the U12 and the U10. While the age groups U12 and U10 are playing on a full size court the age group U9 is the only one playing on a scaled court (Orange-Court). This obviously affects the technical and tactical playing style being closer to adult tennis compared to the other groups. In particular evident was the problem of a too large field (full size court) for the U10. Although taller and physically stronger, their performance parameters differentiated much more from ATP tennis than the U9 ones.

A knowledge discovery framework for the assessment of tactical behaviour in soccer based on spatiotemporal data

ABSTRACT This paper addresses the problem of designing an explanatory computational model for the assessment of individual tactic skills in team sports. The modelling approach tackles the complexity and difficulty of this problem by fusing fuzzy human-like knowledge related to tactical behaviour with time-continuous position data from a tracking system. For this purpose, a hierarchical architecture is proposed. The bottom layer is represented by physically meaningful variables derived from time-continuous position data at specific time instances. Based thereupon, we introduce a temporal segmentation layer that relates the physical variables to game-situation-specific temporal phases. We show how the vague and imprecisely defined linguistic description of the task at hand can be transferred to fuzzy rules in order to get a meaningful temporal segmentation of the time-continuous position data. Finally, the resulting clusters are interpreted in terms of performance indicators in the top layer in order to provide a meaningful explanatory model for the assessment. We show the usefulness of our approach for the task of player evaluation. We do not only provide the coach with a single number to describe the players’ performance but also relate this number to the measurement variables, presenting a more holistic and sophisticated view of the players’ performance.