Edge Detection in Cricket DRS Explained
How caught-behind and LBW edge detection works in DRS reviews, combining Hot Spot, Ultra Edge, and real-time audio.
Why Edge Detection Matters in DRS
Edge detection is the process of determining whether a cricket ball made contact with the bat or glove, primarily in caught-behind and LBW review situations. An LBW appeal requires the ball to have pitched in line, struck the pad in line, and be going on to hit the stumps — but all of that is irrelevant if the ball hit the bat first. Edge detection answers the bat-contact question, and it determines the outcome of a significant proportion of DRS reviews.
The Three-Layer Detection Process
- 1. Visual: slow-motion multi-angle replay reviewed for obvious bat-ball contact
- 2. Thermal: Hot Spot images checked for a bright spot at the bat edge or glove
- 3. Audio: Ultra Edge waveform checked for a spike aligned with the ball's position at the bat
Most Common DRS Edge Scenarios
The most common caught-behind review occurs when the batter appears to have hit the ball but the umpire gives it not out. The fielding side reviews, and the TV umpire uses Hot Spot and Ultra Edge to confirm. The second common scenario is an LBW review where the fielding side has the ball pitching in line and going on to hit the stumps — but the batter may have got a thin inside edge before the pad. Edge detection then determines whether the dismissal is valid.
Improving Edge Detection Over Time
The accuracy of edge detection has improved with each generation of the technology. Ultra Edge's sampling rate has increased from 1,000 frames per second in early implementations to over 10,000 in recent versions. Hot Spot's cameras now capture higher-resolution thermal images in colder conditions. The combination means that 'inconclusive' outcomes are now far less common than they were in the early DRS era (2009–2012).
Frequently asked questions
Can a batter review a caught-behind decision?
Yes. If the umpire gives the batter out caught behind and the batter believes they did not edge the ball, they can use a DRS review. Edge detection is then used to determine whether there was contact.
What if the ball hits the pad and bat simultaneously?
If simultaneous contact occurs, it is treated as the ball hitting the bat — meaning any subsequent LBW appeal fails because the ball hit the bat first.
Does edge detection work on spin bowling?
Yes. Both Hot Spot and Ultra Edge work for spin bowling, though the thin, slow edges from spin can be harder to detect than fast-bowling edges. Glove contact against spin deliveries is more common and is also captured by both systems.