It was 0-0 in the 21st minute of the group match at the FIFA Confederations Cup Russia 2017 between Portugal and Mexico when Pepe opened the scoring – or so he thought. The goal was disallowed, since the Portuguese defender was just offside when Joao Moutinho gave him the ball. The match ended 2-2.
Offside decisions have to be made in a split-second, and they are also a question of perspective. Is the striker really closer to the goal they are attacking than their opponent when they receive the ball from one of their team-mates? The human eye can be influenced in its perception and come to a number of different conclusions based on which angle play is being observed from.
The virtual three-dimensional offside lines that are now available to the video referee and which will be used at the FIFA World Cup™ will provide greater clarity. They are calibrated, computer-generated lines which are projected onto the broadcast image of the field of play. The angle of vision, lens distortion and curvature of the field are all factors that are taken into account by the computer software which then calculates the true position of the offside line.
This technology has been developed via numerous tests and validated by independent third parties. The offside lines that are used are the best and most accurate ones that can be produced using several synchronised camera angles via existing technology. Offside or not? The calibrated lines are available to help the video referee provide the right answer to what could be decisive action in a match.