A soccer ball on a field
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The English Premier League is set to upgrade its existing and acclaimed refereeing technology with a new system that will rely on iPhones to ensure that footballers adhere to the infamous offside rule.
The English Premier League has been using a video referee (VAR) for years to check whether players are offside when a goal is scored in top-flight football matches. The rule, which concerns the position of players when a goal is scored, is difficult enough for officials on the pitch to enforce, prompting the need for a fourth external official.
While VAR relies on an official watching positioned cameras and should theoretically solve the monitoring problem, it has proven less than ideal. Its limitations, including delays and errors, have made it a hated part of modern football.
To avoid the problems with VAR, the League is introducing a new system for the 2024-2025 season. Internally referred to as “Dragon,” Wired reports The system will focus on the iPhone.
Using dozens of iPhones around the pitch, high frame rate video will be captured and fed into a software tool, which allows the smartphones to work together. The video is processed by the system, and can then identify the positions of players.
Spectators along the field
At least 28 iPhones are used in every Premier League stadium, with built-in cameras from the iPhone 14 and newer models are used. Each waterproof case holds up to four iPhones, as well as fans and a power source, and are placed at key points around the field.
It is claimed that the system can easily be scaled up depending on the future needs of the game. If more data is needed on certain parts of the pitch, more cameras can be deployed to collect it.
The result is a system that can track between 7,000 and 10,000 points for each player during a match, compared to systems previously used that could measure 30 to 50 data points for a player.
The system is claimed to be able to reduce the occlusion problem, where parts of a player cannot be seen by any of the positioned cameras due to other players on the pitch and the geometry of the stadium. Part of this is that the system can capture up to 200 frames per second, which beats the 50 or 60 fps rates of broadcast cameras used for VAR.
Average machine
It is even expected that the system will be able to detect upcoming events, such as a potential offside call. When detected, the frame rate can be scaled up for nearby cameras to cover the moment and increase accuracy.
The software that powers it all is based on machine learning. Based on Genius Sports’ work on motion capture in the NBA, the system was trained on several seasons’ worth of football footage to learn when to call an offside.
While the AI will make a call based on what it detects itself, it will not make the decision official for a match. Instead, a human will continue to monitor and make the final match impact call.
Tested, but still needs validation
After the use of VAR, it is likely that football fans will be wary of any new technology being introduced into the game. However, Genius and the EPL believe it has been tested enough.
This included validation by FIFA, who used players in a more traditional motion capture system that was monitored by the system and the data sets were compared. The Premier League is certainly pleased with its accuracy.
“We are confident that by using the latest and most accurate technology we will significantly reduce the time taken for offside decisions, provided the offside rules are applied consistently,” said Tony Scholes, the Premier League’s Chief Football Officer.
Still, football fans are unlikely to have confidence in the system until they see it in practice and see that it works well.