Ball Tracking Technology in Cricket: How Hawk-Eye Works
Ball tracking technology predicts where a cricket ball would have gone after impact for LBW decisions. Learn how it works, its accuracy, and why Umpire's Call remains part of DRS.
What Is Ball Tracking?
Ball tracking uses multiple high-speed cameras positioned around the ground to track the ball's movement through the air, detect its pitch point, and predict its trajectory after hitting the batter's pad. This prediction is used to evaluate LBW decisions — whether the ball would have gone on to hit the stumps.
How Hawk-Eye Works
- Six or more cameras triangulate the ball's position at each frame
- The system detects the ball's seam position, speed, and spin
- At the point of impact with the pad, the system calculates the ball's direction
- Physics modelling predicts the trajectory over the remaining distance to the stumps
- The prediction is displayed as a 3D graphic showing the ball's path
The Three LBW Checks
For an LBW review, Hawk-Eye checks three things: (1) Did the ball pitch outside leg stump? (pitching outside leg means not out regardless of trajectory); (2) Did the ball hit the batter in line with the stumps? (hit outside off from a ball that pitched outside off may not be out); (3) Would the ball have hit the stumps? — either the whole ball misses, clips, or clearly hits the stumps.
Umpire's Call Zone
When ball tracking shows the ball just clipping the edge of a stump or just pitching on the stump line, the system declares 'Umpire's Call'. The on-field decision stands and the reviewing team retains their review, acknowledging that the prediction's margin of error makes the original call defensible.
Frequently asked questions
How accurate is Hawk-Eye ball tracking?
Hawk-Eye is accurate to within 2.6mm on average across its tracking. However, predictions of the ball's path after impact carry more uncertainty, which is why the Umpire's Call zone exists.
Can spin or swing fool ball tracking?
Ball tracking accounts for known swing and spin physics, but sharp late movement (particularly drift after pitching) is harder to model precisely. This uncertainty is built into the Umpire's Call margin.
Why does Umpire's Call sometimes make fans frustrated?
Fans see the graphic show the ball hitting the stumps and expect an out decision. Umpire's Call occurs in a narrow zone where the ball clips the edge of a stump — the prediction uncertainty means the original decision should stand.