Technology

This is how the VAR lines are drawn in an offside

Carlo Ancelotticoach of real Madridcriticized the goal annulled by the VAR to Marco Asensio after the defeat in the ‘clásico’ against FC Barcelona. “We haven’t won because of an offside of which we still have doubts”assured the Italian coach about the lines shot by the video arbitration system –Commanded by Soto Grado from La Rioja-, a method in continuous debate that ended up deciding the game and possibly LaLiga. But, how are the lines drawn to detect an illegal position in Spanish football?



Two ways to draw the VAR lines

As reported Mr. Asubíoaccount specialized in arbitration, in Spain the ‘Hawk-Eye’ system is used‘, as it happens in the main competitions organized by UEFA and FIFA. Two lines are used to detect offsides:

  1. Grid: a two-dimensional line that can be quickly brought in line with the final defender for clear offside decisions

  2. Vanishing Point: these are two lines that are positioned for the defender and attacker

The second assumption is the one used to annul Asensio’s goal that would have made it 1-2 on the scoreboard that a goal from Kessié managed to make it 2-1 almost at the end of the game. In the ‘vanishing point’, “the offside lines are drawn on the parts of the body of attacking and defending players who can be used to score goals“, as explained by the arbitration expert.

Those parts of the body are the same for all the players, goalkeepers included. The lines can also take into account parts raised from the ground, which are shown through a vertical line projected with 3D technology. The positioning of the crosshair is manual, with a line one pixel wide. In this way, VAR can accurately identify the exact position of the offside line and the corresponding body part.



‘Hawk-Eye’, the VAR technology in LaLiga

It must be taken into account that the two lines – the attacker’s and the defender’s – are of different colors. “For offside decisions, after the one-pixel lines are drawn, VAR places transmission lines thicker and where they overlapwill be considered as outside (legal)”, clarifies this ex-referee of national category. At this point it is important to know that what is shared with the spectators is the final image that confirms the decision of offside or not.

As for the system used, the cameras of the ‘Hawk-Eye’ system that are used in each game are calibrated before it. There is a large number of references to be able to reach all parts of the body, regardless of the complexity of the position of the players. In LaLiga there are five cameras: the main one, the two cameras in the penalty area and the two on the goal line.

The key: when the passer contacts the ball

Likewise, ‘Hawk-Eye’ can also use the transmission devices to identify the point of contact with the ball by the attacker. The cameras of the audiovisual system work with 50 frames per second. Therefore, the point of contact with the ball is one of the ‘frames’ that are collected in that precise second.

This was another of the points that generated controversy in the action of the disallowed goal against Asensio. “From the arrival of the VAR, the image must be stopped at the first contact of the passer (in this case Carvajal) with the ball and not when it leaves his foot”, clarifies Mr. Asubío, who also sheds light on a question that generates confusion at first glance. Why don’t the VAR lines sometimes appear straight?



“A lot of it is down to camera angle and perspective. Unless a streaming camera is perfectly lined up with the last defender, the angle of the camera can make you appear to be further back or further forwarde of what in reality is in the drawn horizontal line”, concludes the arbitration expert on the method of the VAR that employs in LaLiga.

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