Motion Capture Study Suggests Improvements for VAR.

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According to the Bath University study, VAR is useful for preventing obvious mistakes but is not yet precise enough to provide accurate judgments every time.

VAR was introduced into association football in 2018 to assist referees in reviewing goals, red cards, penalties, and offsides decisions. It employs film footage from pitch-side cameras to provide VAR operators with a view of the game from various angles in order for them to make decisions on incidents for the head referee, who makes the final decision.

Following several controversial decisions that could change the course of the game, fans and former players have questioned the accuracy and application of VAR.

VAR critics also claim that it disrupts the flow of the game, but some research suggests that it has reduced the number of fouls, offsides, and yellow cards.

Dr. Pooya Soltani of Bath University’s Centre for Analysis of Motion, Entertainment Research and Applications (CAMERA) evaluated the accuracy of VAR systems using optical motion capture systems.

He recorded the 3D positions of the ball and players using optical motion capture cameras while filming a football player receiving the ball from a teammate from various camera angles.

Participants were asked to identify the exact moment of the kick and whether the ball receiver was offside.

According to the study, participants thought the ball was kicked 132 milliseconds later than it actually was, as measured by the optical motion cameras. It was also discovered that when the action was viewed at 0 and 90° angles, and when VAR guiding lines were present, participants made more accurate judgments.

Dr. Soltani stated in a statement, “VAR is really useful in assisting referees in making accurate decisions, but this study has shown it has definite limitations.”

“The frame-rate and resolution of the cameras used in VAR do not always keep up with the fast movements, resulting in blurring of the player or the ball.”

“As a result, the viewer must use their own discretion to extrapolate where the players were at the time the ball was kicked, which affects whether or not it is offside.”

“My research discovered that the ball was kicked 132 milliseconds earlier than the participants perceived, which may not seem like much, but in a fast-paced game it may be long enough for the players to be in a different location, potentially changing the outcomes of offside.”

“This demonstrates that, while VAR is useful for detecting obvious errors, it should not be relied on entirely to make referee decisions.”

According to the study, using higher frame-rate cameras that record the ball’s movement in slower motion could improve VAR accuracy. In addition, thicker guiding lines in the VAR could be used to represent the uncertainty zone for marginal offside decisions. Viewing the gameplay from various angles could also improve accuracy.

On July 20, 2022, Dr. Soltani presented his findings at the 40th Conference of the International Society of Biomechanics in Sports (ISBS).

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