Hawk-Eye, UltraEdge and Hot Spot Explained: Cricket’s Review Technology
What Hawk-Eye, UltraEdge and Hot Spot do in cricket, how they feed the Decision Review System, and what umpire’s call means for lbw and edge decisions.
Modern cricket broadcasts and officiating rely on a number of technologies. Three of the best known are Hawk-Eye, UltraEdge and Hot Spot, each of which provides different evidence to help the umpires. They are used together under the Decision Review System, or DRS, which allows teams to challenge on-field decisions.
The Decision Review System
DRS was first used in international cricket in 2008, in a Test series between India and Sri Lanka, and has since spread to most major formats and competitions. Each team receives a limited number of unsuccessful reviews, with the number set by the match format and the playing conditions. When a captain or batter asks for a review, the third umpire checks the technology and advises the on-field umpire. Whether the technology is available in a particular match depends on the competition and its budget, so not every series uses every tool.
Hawk-Eye
Hawk-Eye is a ball-tracking system that uses several cameras around the ground to follow the ball’s flight. Its software builds a three-dimensional path of the delivery, which it can then project forward. In cricket, it is mostly used for leg before wicket decisions, where the key questions are where the ball pitched, where it hit the batter and whether it would have gone on to hit the stumps.
The graphic displayed on television is a prediction as well as a record, because the last stage of the path after impact is projected. This is why the technology has a margin of error, which leads to the concept of umpire’s call.
Umpire’s call
When Hawk-Eye shows that the ball is only just clipping the stumps, or only just in line, the original decision stands. This is known as umpire’s call. In practice, it means that a not-out decision will stay not out, and an out decision will stay out, if the margin is small. A team does not lose a review if the decision stays because of umpire’s call on the wicket, although it can lose one if the issue is where the ball pitched or impact.
UltraEdge
UltraEdge is a sound-based technology. A sensitive microphone, usually placed near the stumps, picks up noise as the ball passes the bat, pads or gloves. The audio waveform is displayed alongside video footage frame by frame, so the third umpire can see whether a spike in sound coincides with the ball passing the bat. A spike that appears when the ball is passing the bat is evidence of a touch, but the umpire must also check that the noise did not come from the bat hitting the pad or the ground.
A similar system called Snicko is used in some countries and works on the same principle of matching sound to video.
Hot Spot
Hot Spot uses infrared cameras to detect the heat produced by friction when the ball makes contact with a bat, pad or glove. A bright patch on the image can show that contact took place. Hot Spot has been used for edge decisions, though it can miss very fine touches, and because it requires specialist cameras, it is not used in every series.
How they work together
- For a caught-behind appeal, umpires typically look at UltraEdge, and where available Hot Spot, alongside the video.
- For an lbw appeal, they check whether the batter was struck, whether the ball pitched in line and whether Hawk-Eye predicts it would hit the stumps.
- If the evidence is inconclusive, the on-field decision stands.
Why it matters
Review technology has reduced some obvious errors, and it has made decisions more transparent to the crowd. It has not removed controversy entirely, because the technology has limits and umpires still need to judge what the evidence shows.
Frequently asked questions
What does Hawk-Eye do in cricket?
Hawk-Eye tracks the ball using multiple cameras and predicts its path, mainly to help decide leg before wicket appeals.
What is umpire’s call?
Umpire’s call applies when the ball-tracking evidence is too close to overturn the on-field decision, so the umpire’s original decision stays.
How does UltraEdge detect an edge?
UltraEdge uses a microphone near the stumps and shows the sound as a waveform alongside video, so umpires can see whether a noise matches the ball passing the bat.