Accuracy of virtual offside lines put to the test

The fast-paced nature of football grips audiences around the world. Blink and you could potentially miss a decisive pass or the game-winning goal. 

This generates scenarios where referees and linesmen are required to make split-second calls that can, ultimately, prove to be the difference between winning and losing. With the introduction of Video Assistant Referees, officials now have the opportunity to, amongst other scenarios, review close offside decisions in the build-up to a goal. To do so, it is of vital importance that the drawn offside line is as accurate as possible. The recent launch of the Virtual Offside Line Quality Programme (VOL) intends to test this exact challenge of precision, providing Technology Providers with the platform to prove their offside line is accurately drawn.

Deciding when a player is offside might seem a simple task, especially with technology at hand, but there are many technical factors that complicate such calls: the limitations of camera angles, the height of the body part deemed to be offside and the curvature of the pitch all play significant roles. As a result, on 1 July 2019, FIFA launched the FIFA Quality Programme for Virtual Offside Lines with the aim of ensuring technology providers can produce an accurately-drawn line in real-time, whilst taking the above technical factors into account.

In order to receive FIFA-accreditation for their own VOL systems, technology providers have the opportunity to test their products at FIFA-organised events. These events comprise of a number of challenging tests designed to recreate match-like scenarios and test the providers’ ability to produce accurate virtual offside lines within a certain time period. The successful completion of two tests sees the provider awarded FIFA Quality Standard certification for VOL, valid for a period of 2 years. 

It was recently announced that the next of such testing events will take place between 2-5 September 2019, hosted by the La Liga clubs Getafe CF and CD Leganés. 

Figure 1: The above image illustrates the virtual offside lines confirmed by the VAR. The red line indicates the individual body part (excluding hands and arms) that is closest to the goal for the offensive player at the first point of contact with the ball as it is played. The blue line indicates the same as above but for the defensive player.