Goal-line technology is a technical means of instantly determining whether the whole of the ball has crossed the goal line.
Camera-based:
Several approved systems work with cameras that detect the ball and use software to evaluate the footage from all the cameras. In this way, the system can determine whether the whole of the ball has crossed the goal line. Currently licensed systems work with seven cameras per goal installed as high up as possible within the stadium structure.
Magnetic fields:
Several systems operate with magnetic fields. For these systems, cables are placed underground and around the goal, and the ball has elements of the technology inside. The interaction between the receptors in the ball and the magnetic fields created through the underground cables allow the software to calculate the exact position of the ball and determine when a goal has been scored.