How Hawk-Eye tracks one ball

Every US Open court has run Hawk-Eye Live since 2021, with no line judges. Each court has 12 ball-tracking cameras and 6 foot-fault cameras. The cameras film at 340 frames a second. In every frame, at least two cameras see the ball, and the system triangulates where their sight lines cross. It then fits a flight curve through those points to find the bounce.

From the cameras to the player box

At the USTA I was in the stadium working on pro players' data, for players such as Ben Shelton and Coco Gauff and for their coaching teams in the player box, coaches like Brad Gilbert. The feed gives speed, spin, bounce and position for every shot. My job was turning it into the few things a coach can use between points. Coaching from the box has been allowed at the US Open since 2022, with short phrases at the same end and signals otherwise. So the insight has to fit in one sentence.

Ben Shelton, Coco Gauff and Brad Gilbert are likenesses generated with Meshy AI from Wikimedia Commons photos (CC BY-SA); I am generated from my own photos. The points they play are real Hawk-Eye tracking from another player's matches (Rudy Quan, 2025 Indian Wells qualifying, shared with permission), not their own matches. The opponents and the crowd are generic Meshy figures.

What is real here

• The player report and the before/after numbers are illustrative, except "6 of 16", which is from the real tracked match. The locker room and bike are modeled for the story.
• Ball flights and both players' movement: Hawk-Eye L3 tracking via TDI of Rudy Quan's two 2025 Indian Wells qualifying matches, shown with permission and replayed on Armstrong and Ashe with Shelton's and Gauff's likenesses. The serve numbers in the panels are from those matches. The ball and players follow the measured data. The stroke animations are optical motion capture (Visual Analysis Lab, Toyohashi University of Technology; noncommercial use), timed to each measured hit.
• Stadium geometry: an octagonal roof 158.5 m across with a 76.2 m opening, on 8 tripod columns outside the bowl (Sports Illustrated 2015, WSP 2016, ENR 2017). The layout and tiers follow the 2026 USTA seating chart.
• Hawk-Eye figures: Reuters/Gulf Times (2021), CNBC (2023), Hawk-Eye Innovations. The camera mounts at Ashe are not published, so their positions here are an estimate.
• Flushing Meadows and Manhattan: OpenStreetMap buildings (© OpenStreetMap contributors, ODbL).
• Coaching rules: ITF Rules of Tennis 2026, Rule 30. Off-court coaching trial in 2022, permanent from 2025.