Euro 2024: Did the video assistant referee cheat Denmark?

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The decisions of the Video Assistant Referees (VAR) at the European Football Championship are causing heated discussions. In the round of 16 match between Germany and Denmark, an entire nation felt cheated by two video decisions -above all the Danish national coach Kasper Hjulmand .After the match, he vented his anger and criticized the close offside decision that led to a Danish goal being disallowed. Video evidence should not be used, he said, as it was only a matter of centimetres. Only a few minutes after this scene, another video evidence led to discussions: A cross from David Baum grazed the hand of Denmark's Joachim Andersen in his own penalty area, as an analysis of the acceleration sensor in the match ball proved.

The accuracy of the VAR system is now being questioned online ("Denmark ROBBED? Correct decisions?"), while the strict interpretation of the offside and handball rules is also being criticized.

Ultra-wideband sensor in the ball detects handball

The fact that the handball was recognized is partly due to the connected ball technology from Adidas and Kinexon. A 14-gram box with an ultra-wideband sensor (UWB) and motion sensor (Inertial Measuerment Unit, IMU) is installed in the European Championship match ball "Soccer Love". The acceleration sensors measure 500 times per second whether and how the ball has been touched. This makes it possible to determine exactly when the ball touched Andersen's hand. It is therefore undisputed that the ball touched Andersen's hand. But was the touch worthy of a penalty?

Former national team player Michael Ballack has a very clear opinion on this. On Magenta TV, he was outraged by the hand rule, which no longer takes into account intentional or unintentional handball. "How do you want to put your arm down from one meter, he can't even react". He demanded: "We can do away with this deflection thing [...] right away." Instead, we should use common sense and find a rule or an interpretation of when it is a penalty-worthy handball - ignoring the fact that this has been the subject of debate for decades.

Former England striker Alan Shearer was quicker to sum up his criticism on X:

Before the introduction of VAR, meanwhile, the German soccer nation would have denounced referee Michael Oliver's decision if he had used his discretion and not given a penalty. Now he has not only been sharply attacked by the Danes for relying on video evidence.

Twelve cameras track 29 points on the players' bodies

While the handball was both visible and measurable, the offside decision mentioned at the beginning was probably hardly recognizable for the linesman, as the Dane Thomas Delaney was actually only a foot's width offside when the ball was passed.

On X, TikTok and other social networks, however, the accuracy of the system is questioned, as the twelve cameras mounted under the stadium roofs only take 50 images per second, which is too inaccurate for a centimeter-precise decision. This would be correct in principle if there was only one camera. However, because the system combines the images from several cameras to create a 3D model, the accuracy can be significantly increased. Using algorithms from the "SkeleTRACK" AI framework from Hawk-Eye, 29 body points are recorded for each player and a 3D skeleton is calculated from them in real time.

AI recognizes limbs and assigns them to players

In confusing game situations, when bodies overlap, it is a challenge to assign the limbs to the right players. This is where artificial intelligence comes into play: specially trained deep learning algorithms, known as deep convolutional neural networks, have been trained to recognize body parts and assign them to a skeleton using thousands of sample images.

From the combination of the 3D skeletons of all 22 players on the pitch, the system then calculates whether a pass was offside or not. The decision is then visualized in a 3D animation and presented to the referee and spectators. FIFA explains the Semi Automatic Offside Technology (SAOT) in a YouTube video, which unfortunately cannot be embedded on other websites.

Another point of criticism from the Danish coach and on social media: even if the system works accurately enough to determine the player's position down to the centimeter, you still don't know when the ball has left the foot of the crossing teammate. However, thanks to the acceleration sensors in the ball already mentioned in the handball detection, this is known very precisely, as the sensor determines an acceleration value every 0.002 seconds. The VAR freezes the positions of all players at the time the ball is released and determines to the centimeter whether there are still two players from the other team between the attacker and the opponent's goal. Typically, this would be a field player and the goalkeeper.

Game flow suffers due to long breaks

Although the complex tracking system and the sensors in the ball help to minimize wrong decisions, they lead to new discussions and are still far from being accepted, as became clear in yesterday's round of 16. One thing is undisputed: the flow of the game is interrupted for longer by the video evidence - fortunately, the VAR now works much faster than when it was introduced a few years ago.

Thanks to the video assistant referee, however, referees can also allow moves to run longer and only check whether there have been any infringements of the rules after they have been completed. As a result, more goals are scored, which are subsequently disallowed all the more frequently than before. It's not just Denmark fans who are likely to wonder whether this technical interpretation of the rules is good for soccer. The heated debate about the use of VAR will probably not be over for a long time yet, even with even more precise systems.

(vza)