Cricket Technology: Hawk-Eye, HotSpot, UltraEdge and How They Changed the Game
Modern cricket uses several technology systems to assist with umpiring decisions through the DRS (Decision Review System). Hawk-Eye (ball tracking) predicts whether a ball would have hit the stumps for LBW decisions. HotSpot (infrared imaging) detects heat from bat-ball contact for caught behind and bat-pad decisions. UltraEdge (snickometer) detects ball-bat contact from audio waveforms. Each system has accuracy limits that have created controversy, including the famous 'umpire's call' controversy.
DRS technology overview: the Decision Review System (DRS) uses multiple technology tools to assist the third umpire in reviewing on-field umpiring decisions. The main systems used in international cricket: (1) Hawk-Eye (ball tracking) — tracks the ball's path from the bowler's hand through its trajectory after pitching, using multiple high-speed cameras; specifically used for LBW decisions to predict whether a ball would have hit the stumps; (2) HotSpot (infrared thermal imaging) — captures heat generated by friction at the moment of contact; used to detect whether the ball touched the bat or the inside edge before reaching the wicketkeeper; (3) UltraEdge (previously called Snickometer or Snicko) — uses a high-sensitivity microphone to detect sound spikes at the moment of potential bat-ball contact; works alongside HotSpot for caught-behind and bat-pad decisions.
Hawk-Eye and LBW
How Hawk-Eye works for LBW: Hawk-Eye uses 6-10 cameras positioned around the ground to track the ball's trajectory in 3D. For LBW decisions: (1) The system tracks the ball from the moment it is bowled; (2) When the ball hits the batsman's pad, Hawk-Eye calculates the ball's predicted continuation (where it would have gone without the pad in the way) based on its tracked velocity, spin, and deviation from the pitch; (3) The third umpire sees a graphic showing whether the ball would have hit the stumps, missed above, or missed outside the off or leg stump. The accuracy limitation: the further the ball has to travel from where it hit the pad to the stumps, the greater the uncertainty in Hawk-Eye's prediction. The 'umpire's call' zone exists because Hawk-Eye has a published accuracy of ±2.5cm — so a ball predicted to hit the edge of the stumps within that margin is called 'umpire's call' (the on-field umpire's decision stands).
Ball Tracking Accuracy
Ball tracking accuracy and limitations: Hawk-Eye's ball tracking is used not just for DRS but also for cricket broadcasts — showing the full trajectory of every delivery in statistical overlays, pitch maps, and bowling wagon wheels. The accuracy limitations: (1) Spin prediction — once the ball has pitched and turned, predicting its further trajectory requires modelling the spin's effect; this is less certain than tracking the pre-pitch trajectory; (2) Swing prediction — in conditions where the ball is swinging, the post-pitch trajectory prediction accounts for air resistance but may not perfectly capture late swing; (3) umpire's call zone — the ICC set a 50% threshold: if Hawk-Eye shows less than 50% of the ball hitting the stumps, it is 'missing stumps'; if 50-100% of the ball is hitting, but the prediction carries uncertainty (edge of the stump predictions), it triggers 'umpire's call.' Full hits (ball clearly hitting the middle of the stumps) are overturned regardless.
Technology Future
Future cricket technology: several developments are under consideration or in trial for further improving cricket officiating: (1) Real-time ball tracking for umpires — instead of only the third umpire seeing ball tracking on review, providing the on-field umpires with LBW predictions through an earpiece in real-time (removing the need for player reviews for LBW); (2) Automatic wide/no-ball detection — using tracking systems to automatically call wides and no-balls without umpire judgment (similar to tennis's Hawk-Eye Cyclops for service calls); (3) AI-assisted run outs — using multiple cameras and AI to determine crease line positions more accurately than human third umpire review; (4) Wearable tracking for fielders — GPS and acceleration sensors on fielding players for real-time position data (already used in some domestic competitions for broadcast and coaching). The ICC trials technology in lower-tier ICC competitions before considering it for international implementation.
Frequently asked questions
How does Hawk-Eye work in cricket?
Hawk-Eye is a ball-tracking system used in cricket DRS (Decision Review System) to adjudicate LBW decisions. It works using multiple high-speed cameras (typically 6-10) positioned around the cricket ground, all focused on the playing area. The cameras track the ball's trajectory in real-time from the moment the bowler releases it. When an LBW decision is reviewed: (1) Hawk-Eye calculates where the ball pitched (inside or outside the batsman's leg stump — balls pitching outside leg cannot be LBW); (2) It tracks where the ball hit the batsman's pad and calculates the ball's predicted trajectory if the pad had not intervened; (3) A 3D graphic shows the predicted ball path continuing to the stumps — showing whether it would have hit the stumps, missed above, or missed to the side. If the predicted ball path shows the ball hitting the stumps, the decision is overturned to out. The 'umpire's call' zone applies when the prediction shows the ball clipping the edge of the stumps within Hawk-Eye's accuracy margin of ±2.5cm.
What is the difference between HotSpot and UltraEdge in cricket?
HotSpot and UltraEdge are both used in DRS (Decision Review System) to detect whether the ball made contact with the bat, but they work using completely different methods: HotSpot uses infrared thermal imaging — when the ball contacts the bat, the friction generates heat; cameras sensitive to infrared radiation capture this heat signature as a bright mark on the bat or glove (visible to viewers as a glowing spot in the HotSpot replay image). The limitation: very light edges ('feather edges') may not generate sufficient heat for HotSpot to detect. UltraEdge (Snickometer) uses a highly sensitive microphone (or stump microphone) to detect the sound of ball-bat contact — a sharp click or spike in the audio waveform at the moment the ball passes the bat indicates possible contact. The limitation: various other sounds (ball hitting pad, clothing rustling, footsteps) can also create audio spikes. The ICC uses both systems together for caught-behind decisions — both must agree for a clear verdict.
What is umpire's call in DRS?
Umpire's call in DRS (Decision Review System) is the outcome when technology (specifically Hawk-Eye ball tracking for LBW decisions) shows that the decision could go either way — the ball is shown to be in a marginal zone where the original on-field umpire's decision stands. For LBW: umpire's call occurs when Hawk-Eye predicts the ball is hitting the stumps, but less than 50% of the ball's predicted cross-section is clipping the stump edge — meaning the ball is on the borderline of hitting. In this case, the third umpire rules 'umpire's call' and the original on-field decision stands (if the on-field umpire gave not out, it remains not out; if they gave out, it remains out). Additionally, when umpire's call is the outcome, the reviewing team retains their DRS review (it is not consumed). The umpire's call concept exists because Hawk-Eye has a known accuracy limit of approximately ±2.5cm, and decisions within that accuracy margin should not override the human umpire's judgment.