Cricket Technology Explained: Hawk-Eye, Snickometer, UltraEdge, and How DRS Works
The complete guide to cricket's ball-tracking and edge-detection technologies — Hawk-Eye's ball trajectory prediction (LBW reviewed via DRS), Snickometer (now UltraEdge) for edge detection via sound and vibration, Hot Spot infrared imaging, Real-time Snicko, how DRS reviews are adjudicated, and why Umpire's Call exists.
The Decision Review System (DRS) transformed cricket officiating from 2009 onward by supplementing on-field umpire decisions with three distinct technologies: ball-trajectory prediction (Hawk-Eye), edge detection (UltraEdge/Snickometer), and heat imaging (Hot Spot). Each technology serves a specific review function and has defined limitations. Understanding how each works — and why they sometimes produce controversial outcomes — is essential to following modern cricket officiating.
Hawk-Eye: Ball-Tracking and LBW Prediction
Hawk-Eye: a ball-tracking system using 6-7 high-speed cameras positioned around the ground. Each camera tracks the ball from the moment of delivery. The system: (1) tracks actual ball position through the air before pitching (where did the ball pitch — in line with the stumps or outside leg stump? LBW law requires the ball to pitch in line or on the off side of the stumps for a right-handed batsman); (2) tracks the ball's position at the moment it hits the batsman (was the impact in line with the stumps?); (3) predicts where the ball would have gone if the batsman were not there (would the ball have gone on to hit the stumps?). Step 3 is the prediction — it is not measured directly, it is calculated using the ball's trajectory, spin, seam position, and pitch characteristics. This prediction is why 'Umpire's Call' exists: at the margin of the prediction (ball predicted to clip the top of the stumps, or just hit the side of leg stump) the uncertainty of the model means the on-field umpire's original decision stands, rather than the marginal prediction of the model.
UltraEdge (Snickometer): Detecting Edges
Snickometer (invented by English scientist Allan Plaskett, first used in cricket TV broadcasts in 1999) was the original edge-detection system: it combined: (1) a stump microphone recording the sound of the ball; (2) an oscilloscope trace showing amplitude of sound over time. A spike in the oscilloscope trace synchronized with the moment the ball passed the bat edge indicates a nick. Snickometer's limitation: it was slow (required replaying footage frame by frame to sync sound with visual) and was originally used only in broadcast, not in umpiring decisions. UltraEdge (introduced in DRS in 2014): the real-time successor to Snickometer. It uses multiple stump microphones, synchronises the audio waveform with the ball's position in real time, and presents the result in seconds. Hot Spot: an infrared imaging system that detects heat generated by friction — if the ball brushes the bat edge, a bright spot appears on the bat (or pad, or glove) at the point of contact. Hot Spot is expensive (requires two infrared cameras, proprietary technology) and not used in all DRS implementations. Some cricket boards (including BCCI for IPL) have declined to use Hot Spot, relying on UltraEdge instead.
How a DRS Review Works: Step by Step
A DRS review sequence: (1) On-field umpire makes a decision (out or not out); (2) Within 15 seconds, the dismissed batsman (if out decision) or bowling captain (if not out decision) signals the review request — a rectangular 'T' gesture with hands; (3) The third umpire (in a TV van at the ground) takes control; (4) For LBW reviews: Hawk-Eye checks pitch location, impact location, and runs the trajectory prediction. UltraEdge (and Hot Spot if available) checks for a possible bat or pad edge — if an edge is detected, the ball hit bat or pad rather than pad alone, which changes the LBW analysis; (5) The third umpire reports findings to the on-field umpire via earpiece; (6) Decision: the on-field decision is overturned if the technology clearly shows the original decision was wrong. If the outcome is marginal (Umpire's Call) — meaning Hawk-Eye predicts the ball is clipping the stumps rather than clearly hitting them — the original decision stands; (7) Review outcome: teams start with 2 DRS reviews per innings; an unsuccessful review (decision stands) costs 1 review; a successful review (decision overturned) retains the review.
Frequently asked questions
What is Hawk-Eye in cricket?
Hawk-Eye is a ball-tracking system using 6-7 high-speed cameras to track the ball's trajectory. In cricket, it is primarily used in DRS (Decision Review System) for LBW reviews: it tracks the ball's pitch position, impact position on the batsman, and predicts where the ball would have gone if the batsman were not there. The prediction of future trajectory (step 3) is calculated rather than observed — this uncertainty is why 'Umpire's Call' exists for marginal decisions. Hawk-Eye was first used in cricket in 2001 (broadcasters) and in DRS officiating from 2009.
What is the difference between Snickometer and UltraEdge?
Snickometer (1999) was the original edge-detection system used in cricket broadcasts — combining stump microphone audio with an oscilloscope trace to detect bat-ball contact by identifying sound spikes. It was slow (required frame-by-frame analysis) and not used in real-time officiating. UltraEdge (2014 in DRS) is the real-time successor: using multiple synchronised microphones and presenting audio waveforms alongside ball-tracking video in seconds. UltraEdge is now standard in ICC DRS. Hot Spot (infrared imaging showing heat from bat-ball friction) is an additional system used in some DRS implementations but not universally (not in IPL, not in some lower-budget series).
What is Umpire's Call in cricket?
Umpire's Call is a DRS outcome for marginal LBW decisions — when Hawk-Eye predicts the ball would hit the stumps but only by a small margin (a fraction of the ball's width clipping the outside of leg stump, or the ball clipping the top of the stumps). In Umpire's Call situations, the original on-field umpire decision stands — because the Hawk-Eye prediction is not certain enough (the margin of error in the prediction model is larger than the margin by which the ball was predicted to hit the stumps). Umpire's Call applies to: the pitch zone (was the ball pitched in line?), the impact zone (was the ball hitting the bat in line?), and the stumps zone (would the ball have hit the stumps?).