Hawk-Eye Ball Tracking in Cricket: How It Works & LBW Reviews

Hawk-Eye is the ball-tracking technology used in cricket's Decision Review System (DRS) to evaluate LBW decisions. Originally developed for tennis line calls, it was adapted for cricket to track the trajectory of the ball from the bowler's hand through to where it would theoretically travel after hitting the batter's pad. It has become the most discussed — and debated — cricket technology in use.

How Hawk-Eye Works

Hawk-Eye uses six or more high-speed cameras positioned around the ground, each capturing the ball's position many times per second. A computer reconstructs the ball's three-dimensional trajectory from these multiple angles. For LBW reviews, Hawk-Eye calculates: 1) where the ball pitched relative to the stumps; 2) whether the ball would have hit the stumps if the pad was not in the way; and 3) the line at which the ball struck the pad.

The Three LBW Tests

Hawk-Eye evaluates three elements for an LBW decision:

1. Pitching: the ball must pitch in line with the stumps (between off and leg stump extended) or outside off stump. If the ball pitches outside leg stump, the batter cannot be LBW — Hawk-Eye confirms this instantly.
2. Impact: the ball must hit the batter's pad in line with the stumps. Hawk-Eye shows whether the impact was in line or outside off stump.
3. Hitting the stumps: this is the most complex part — Hawk-Eye models the ball's continuing trajectory past the pad to determine whether it would have hit or missed the stumps.

Umpire's Call Explained

The ICC's 'umpire's call' zone is the area around the edge of the stumps and the margin of ball-tracking error. If the predicted trajectory of the ball clips the edge of the stumps within the umpire's call margin, the on-field umpire's decision is upheld — whether out or not out. This reflects the technology's acknowledged margin of uncertainty: the Hawk-Eye prediction has an error range, and within that range the umpire's call stands.

Common Controversies

• Ball deflection after impact: Hawk-Eye assumes the ball travels in a straight line after hitting the pad. In reality, spin and seam can slightly deflect the ball on impact — creating small inaccuracy.
• Umpire's call frustration: when Hawk-Eye clearly shows three reds (pitching, impact, hitting) but the umpire's call saves a batter, fans and players often find the concept confusing.
• Accuracy of prediction: Hawk-Eye's manufacturers acknowledge a 2–3 mm margin of error in prediction over the final metres of travel — the umpire's call zone was set to account for this.
• Visual display: the red/yellow/green graphic on broadcast TV is an approximation — the actual data is more nuanced.

Other Hawk-Eye Uses in Cricket

• Wagon wheel: mapping where each shot went around the ground.
• Pitch map: showing where the ball has landed in an over or spell.
• Beehive: density chart of delivery landing zones over a session or innings.
• Stump vision: the camera in the stumps — providing unique angles of deliveries.

Scenario: A right-arm spinner bowls a delivery that hits the batter on the front pad. The umpire says not out. The bowling team reviews. Hawk-Eye shows: pitching in line, impact in line, hitting off stump — but only clipping the edge of off stump within umpire's call. Because the on-field umpire said not out, the decision stands despite three yellow indicators. The review is retained because umpire's call applies.