Semi-automated offside technology (SAOT) will be in action in the EFL Play-Off Finals at Wembley this weekend.

SAOT will provide more efficient placement of the virtual offside line, based on optical player tracking, and produce virtual graphics to ensure an enhanced in-stadium and broadcast experience for supporters. The operation of semi-automated offside technology does not change the accuracy of the decision making but enhances the speed, efficiency and consistency of the process.

The Premier League has worked in collaboration with PGMOL and sports data and technology company Genius Sports to develop a new SAOT system – and this will be its first use in EFL competition.

What is semi-automated offside technology?

SAOT is a support tool that automates key elements of the offside decision-making process for the video assistant referee (VAR). It will be used in close offside calls – to either confirm or recommend a change to the referee’s call on-field – as is currently the case with VAR.

To determine close offside calls, the VAR currently needs to work with replay operators (RO) to manually determine the ‘kick-point’ for the offside decision and then ‘draw’ calibrated lines with a crosshair on the relevant defender and attacker, using multiple camera angles. Once the lines and kick-point are determined, an ‘offside’ or ‘onside’ decision is generated.

SAOT will suggest a ‘kick point’ and automatically create offside lines on the second rear-most defender and the relevant attacker, saving significant time in determining whether a player is onside or offside. Once the SAOT-generated outcome has been reviewed and approved by the VAR, a decision visual will be automatically generated and distributed to fans in the stadium and to the media.

How does the system work?

The system uses up to 30 newly-installed cameras mounted around Wembley, with several capturing footage at 100 frames per second, twice the frame rate of typical broadcast cameras.

The cameras track the exact movement of the ball as well as up to 10,000 surface ‘mesh’ data points per player, meaning the technology will track to see if any attacking player involved in the build-up to any incident was offside. These are then ‘flagged’ automatically in the SAOT software to the VAR and SAOT operator.

Why isn't it fully automated?

The technology is ‘semi-automated’, meaning there is human input as the VAR still needs to confirm the decision and that the SAOT system has accurately identified the ‘kick-point’ and the correct players with the correct part of the body, and the outcome of the SAOT.

VAR will also need to determine whether the referee needs to conduct an on-field review for ‘subjective’ offside calls – such as cases where a deliberate play by a defender needs to be considered, or where an attacking player doesn’t touch the ball but could be interfering with an opponent whilst in an offside position.

Will SAOT rule out more goals for offside?

No – SAOT will not affect the accuracy of the decision-making or change offside calls. In the Premier League this season, offside calls have been adjudged to be 100 per cent correct.

It will enhance the speed and efficiency of the process. The expected average reduction of decision time in close offside calls with SAOT is approximately 30 seconds.

What will the SAOT decision visual look like?

Once the decision is made – a decision visual will be sent to broadcast and giant screens in stadiums.

This will feature a 3D virtual replay of the relevant players, identifiable by each team’s kit. An offside decision will be shown with a red line and onside with a green line. A white vertical wall will represent the offside line, with a blue ‘pulse’ on the defender’s relevant body part.

When an attacker is offside, the part of their body which is offside will appear through the white wall and be outlined in red. The final image in the virtual replay will be on an angle, off-centre, to provide a clear view of the attacker and defender involved in the offside review and the ‘pulse’ will no longer be displayed.

There will be no overlay with broadcast footage – the replays will cut away to the decision visual. This allows for the decision to be displayed as quickly as possible.

How Semi-Automated Offside Technology works

How Semi-Automated Offside Technology works