Table 7.1 Comparative table of EPTS systems used in team sports Communication
systems
Advantages Disadvantages
LPS High number of
measurements.
Great accuracy when gathering data in real time.
Use of ultra-wide bandwidth that reduces interference in transmission.
Fixed, lengthy and costly installation.
Camera –
PC connected to customers is also used, thus facilitating the exchange of information via cable.
image
Figure 7.6 Example of two camera-based ball tracking system.
In Figure 7.7 we find another example of synchronization between cameras and internal communication between the different elements (Martinez-del-Rincon et al., 2009). Thus, in summary, eight cameras with partial view overlapping of several of them on the pitch are divided up into two groups of four, with each group being connected to a PC and the four cameras being synchronized according to the group using the video capture card. The two PCs are synchronized via an ad-hoc two wireless network (WIFI), which synchronizes the clocks on the two PCs.
image
Figure 7.7 Network architecture of an eight camera-based sports player tracking system.
By using the previous examples as a reference for usual sports player tracking system architectures together with other elements involved in play in team sports, it can be seen that data transmission methods are not so complex. This is because in most cases the transmission required in these systems is by video, from cameras to the PC or PCs that need to analyze the images, process the data obtained from them, undertake tracking and generate output to ensure it is displayed.
Wireless Body Area Networks in Team Sports
In this section, the authors have based their work on four popular sports, namely football, rugby, basketball and hockey, to demonstrate the use of EPTS in team sports and the measurements provided by each of them (see Chapters 2, 3, and 4).
Some of the measures that allow to extract the mentioned EPTS are the
player's position on the field, the instantaneous speed, the instantaneous
acceleration, and the total distance traveled,
As can be seen in Table 7.2, the precision of these measurements, depending on each of the tracking and positioning systems, is different. LPS is the system that offers minor errors in the first three measures, having in counterpoint to the GPS that even being the cheapest because it does not require installation, it has major errors.
Table 7.2 Comparison System Player
positioning errors
Instantaneous speed errors
Instantaneous acceleration errors
Total distance error
LPS 23±7 cm 0.25±0.06 m/s 0.68±0.14 m/s
24.0%
GPS 96±49 cm 0.28±0.07 m/s 0.67±0.21 m/s
22.2%
VID* 56±16 cm 0.41±0.08 m/s 0.91±0.19 m/s
22.7%
The final transmission of the data from the EPTS to the servers where they are analyzed and processed is carried out via high-speed wireless (WIFI) or wired (Ethernet) networks, in order to offer the expected service.
As a last point, it must be remembered that the systems mentioned (mainly GNSS/GPS), are also useful in other (individual) sports, such as cycling, running, rowing, or cross-country skiing; they are endurance sports in which the athlete moves from a starting point to a predefined point, and the measures described are equally valid.
Lesson Learned and Concluding Remarks
In this section we will discuss and compare the different transmission systems used in the various team sports, and the reasons why they have been chosen for use.
The sports that have started to make use of these technologies are mainly
those considered mainstream sports, and/or in high level competitions (e.g.,
World Cup in Russia or UEFA Champions League). Those with less media
coverage, less economic resources, or simply because they are considered
alternative team sports, have not started using SPTS even though they could
benefit from its advantages, due to the high cost and the need for qualified
technical staff to analyze the data they provide. On the other hand, the most popular team sports, or those with the largest number of followers, take advantage of the data collected to provide a wealth of information for the transmission of matches in real time, to provide the technical staff with information to improve group strategies or individual performance, or even to create platforms for fans to consult all kinds of interesting information.
The great influence of the use of positioning and tracking technologies in team sports comes from the United States, where their use has been widely accepted among fans of national sports such as basketball or American football, where we can see great advances, and many of the data generated by EPTS are open data and even the result of competitions for data scientist.
Semi-automatic multiple camera video systems (VID), radio-based local positioning systems (LPS) and global positioning systems (GPS) have become indispensable technologies for evaluating physical and tactical behavior in both training and competition (Linke et al., 2018). It is important to note that, for team sports, each positioning system has its advantages and disadvantages that must be considered with respect to the specific objectives (Hoppe et al., 2018).
Depending on the sport, the use of certain technologies is limited by the location of the sport. Sports like basketball cannot benefit from GPS transmissions, as the signal is often weak indoors. Therefore, they benefit from LPS for the transmission of the data obtained, as it has proved to be a valid and reliable method to monitor distance and time of operation at constant speeds (Colino et al., 2019). The size of the field facilitates the placement of the locators and the sensors used are not intrusive for basketball practice, as they are placed at the waist in the back of the trousers (Colino et al., 2019).
On the other hand, GPS is one of the most cost-effective and efficient options in the open field, used in both football and football. Its use has become a popular option, since it can be used to track an individual’s speed and distance without the rigidity of other tracking systems (Hamilton, 2017). The system lacks its own facility, making it easy and cheap to use.
Systems such as LPS are no longer effective in sports with large and contested playing fields
In the case of American football, the use of these devices has been
extended to both matches and training sessions. The players include two
sensors on the shoulders and under the guard. Additionally, sensors are included on the ball to complement the data obtained.
In addition, semi-automatic multiple-camera video systems are also used in football, which allow the player to be tracked and monitored, with worse results than those offered by GPS (Linke et al., 2018), but being less invasive and giving the possibility to make more complex analysis of the game.
The systems are used both in training and in matches since the data collected offer innumerable possibilities to the technical team. And, usually, those sports that make use of one technology do not combine it with others.
That is, if they make use of GPS in matches.
Table 7.3 shows a comparison between the three most widespread
positioning and tracking systems and their use among the chosen
mainstream sports: basketball, football and American football.
Table 7.3 Comparison between sports
Sports LPS VID GPS/GNSS
Basketball This is the best system, as it covers smaller surfaces, and the game is very
dynamic.
Offers the best results in terms of positioning and
instantaneous speed.
Implementation possible, although it is not the most suitable system, owing to its positioning,
acceleration and instantaneous speed faults.
Impossible to implement as it is played in an enclosed space and so
the GPS
signal is poor.
Medium to high risk of error when positioning a small field such as a basketball court.
Soccer Large, more
costly
surfaces and difficult to implement.
Great margin for error in terms of total distance.
Implementation possible, although it provides worse results than the GPS.
May be
possible to implement when play is on an open pitch.
Good results in terms of speed and instantaneous acceleration.
American football
Large, more costly
surfaces and difficult to implement.
Not very reliable in long runs.
Implementation possible, although like soccer, the GPS provides better results.
May be
possible to implement when play is on an open field.
Fairly
reliable.
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8 Real-Time Feedback An Update
José Pino-Ortega, Asier Los Arcos and Markel Rico-González
Introduction
Real-time feedback could achieve a competitive advantage for team sports (Glazier et al., 2003). Until a few years ago, players’ movement patterns were analysed through notational motion analysis (i.e. video-based tracking, computer based tracking, and the use of electronic transmitters) (Dogramaci et al., 2011). These technologies, based on videotaping players (Dogramaci et al., 2011), were often utilized after the session or match with only one player being tracked at a time (Carling et al., 2008; Scott et al., 2015). Specifically, the players were videotaped for reference purposes whilst performing particular activities in order to provide calibration values. The video tapes were played back on a TV screen and coded for various match activities (Carling et al., 2008), fundamentally, movement patterns. The calculation was made by recording the duration of each activity, total time summed, and frequency of activity calculated according to separate time blocks. The distance covered in each activity within each time block was the product of mean velocity and total time spent in the activity (Carling et al., 2008). The total distance covered during a match was calculated as the sum of the distances covered during each type of locomotor activity (Carling et al., 2008). So, in addition to the hard work, this analysis process had some limitations. For example, the time taken to complete the analyses, the definition of movement categories, and the parallax error or lack of reliability due to the impossibility of eliminating subjective analysis (Aughey & Falloon, 2010). Moreover, the feedback with this technology was carried out after the session or match. Thus, it did not allow the feedback during the session or match and the coaches could not assess the development of their strategy objectively.
New technologies were suggested due to the need to improve the technology and avoid the errors of notational analysis. For example, the use of multiple semi-automatic high-definition cameras (VID) is a method for analysing player´s and team´s performance based on a set of cameras placed around the field (Pons et al., 2019). This system allows researchers to access the trajectory data to assess players’ performance and the interaction among them (Bartlett et al., 2012; Pons et al., 2019). Until 2014, the use of this system was more common and several articles analysed the competition through the VID (Rico-González et al., 2019).
Although VID technology is frequently used on match days, it is not as common in training sessions due to difficulties related to the installation and maintenance of cameras in training facilities (Bastida-Castillo et al., 2019). The limitation for analysing performance during the training process by VID was resolved using Global Positioning Systems (GPS) or Global Navigation Satellite Systems (GNSS). In addition, although they are also used on outdoor fields (Bastida-Castillo et al., 2019), Local Positioning Systems (LPS) were created to alleviate the GPS limitation in the field of indoor positioning (Alarifi et al., 2016). Radio-frequency technologies also include microelectromechanical sensors (MEMS), which make neuromuscular variables available. Until a few years ago, these technologies (i.e. GPS/GNSS and LPS) were not allowed to be used during competition, but today team sport federations such as those for soccer, Australian football or rugby allow the use of radio based technologies during matches and thus their utility has increased (Rico-González et al., 2019).
As an example, in soccer the International Federation of Association Football (FIFA) has recently adapted its rules in favour of the technology. In 2015, FIFA took the initiative to create the department of Electronic Performance and Tracking Systems (EPTS). Specifically, as a result of the insistence of the football clubs, in 2015 the International Football Association Board (IFAB) published a circular in which it communicated the modification of rule 4 (i.e. the equipment of players) of the FIFA regulations for competition. In relation to this progress, IFAB invited the sector of suppliers of techno accessories in Zurich (Switzerland) to present their products and services. On 2 July 2017, German and Chilean teams participated in a pilot study during the final of FIFA’s Confederations Cup with the aim of providing greater knowledge about the potential benefits of using technology within the technical area. The impact of the use of the technology was analysed in real time, providing statistics (indicators of technical–tactical and physical performance) and images during the game. After this, the regulations have allowed viewing on the bench in real time. This can help the technical staff to construct better solutions (Le, 2016) in situations that might need swift action from the coaches (Andreassen et al., 2019).