Goal-line technology works by employing two separate detection methods: GoalRef and Hawk-Eye. GoalRef makes use of electromagnetic antennae set up to frame each team’s goal. As soon as the entire ball has made it across the line, a signal is pinged to a referee’s smart watch to either make the call for him, or corroborate the goal call he has already declared.
The Hawk-Eye method uses up to eight high-speed cameras to further prove that a ball has completely crossed the goal line before making a call. The cameras feed footage to a processing system that overlays the images from multiple angles along with dots on the goal posts and crossbar to recreate the moment in computerized 3D.
Referees in any sport have a hard job, but the reactions to bad calls in World Cup or League finals matches can get ugly. Having the tech available as a resource to inform and back up referees calls gets a lot of attention at league finals, regional cups, and of course the world cup. But bringing the same level of accuracy to season matches will create more consistent calls and a tech-boosted referee authority that will hopefully eliminate discrepancies. It’s working well for the Premier League — it’s been using goal-line technology since the 2013-2014 season.