Goal, or not?
At the 2010 World Cup, Frank Lampard was denied a goal against Germany even though the ball was clearly over the line. Partly because of mistakes like this, the laws of football allowed goal-line technology from 2012. A system of 14 high-speed cameras, seven trained on each goal, tracks the ball and sends a signal to the referee's watch within a second confirming a goal. You'll find similar technology in tennis.
The VAR video referee
In a room full of screens sit referees watching the match through dozens of cameras. They step in for only four types of situations: goals, penalties, straight red cards and mistaken identity. VAR was first used at a World Cup in 2018, in Russia.
A chip in the ball and semi-automated offside
At the 2022 World Cup in Qatar, the Al Rihla ball had a sensor at its centre sending data about its movement 500 times a second. Combined with 12 cameras under the stadium roof tracking 29 points on each player's body, this produced semi-automated offside: the computer flags an offside and the referees simply confirm it. Viewers are then shown a 3D animation of the situation.
GPS vests and data
Professional players train in vests carrying a GPS device and motion sensors between their shoulder blades. It measures distance covered, number of sprints, acceleration and, with a chest strap, heart rate too. Clubs and academies in Italy, England and Germany use this data to plan training and estimate when a player is at risk of injury. Young players thus grow up from the start with wearable electronics and video analysis.