As an engineering student with the opportunity to take a placement year in the middle of my studies, I chose to work at Hawk-Eye Innovations Limited. With ever more tennis events looking to have Hawk-Eye on their courts, I have been on a busy schedule with the tennis system throughout my placement year. Reaching the twelve month mark of working various tennis events has brought me a unique insight to the world of Hawk-Eye, some of which I will share in this blog.
When arriving at a new stadium, one of the first things to set up is the cameras which track the ball through play. Each Hawk-Eye court will have a total of 10 cameras around the stadium, with 5 cameras focused on one side of the court and the other 5 trained on the opposite side. Having this many cameras allows the ball to be tracked at all times, even when the player may be positioned such that they obscure some views.
These 10 cameras all work together to provide tracking of the ball from the very first serve to the final winning point of each match. Every camera provides a 2D position of the ball as it travels across the image, combining these 2D positions together via triangulation produces a 3D location of the ball within the court. As all cameras are kept in sync by a gen-locking signal, time may be factored in to create the complete track of the ball throughout the point in play. It is therefore possible to record every single bounce of the ball should the players wish to stop play and challenge a line call within reasonable time.
Not all courts are made equal, slight variations in the painting of the lines and how flat the court is can change a shot from a winner to an error by a matter of millimetres. To account for this we will measure every dimension of the courts lines and then use a laser to determine the undulation of the court. When staring down a line at ground level it is surprising just how much height variation there is on what most people assume to be a perfectly flat surface. These are just some of the factors Hawk-Eye takes into account to be so consistently accurate.
If you ever catch the Hawk-Eye team on a court with a box of balls you will soon see an interesting display of carefully placed tennis balls in precisely measured positions. Beyond looking quite intriguing this is actually one of the most important parts of setting up the Hawk-Eye system. Using these 70 or so balls, we can begin the calibration process that allows for all of the 10 cameras to be tuned such that they will successfully work together to give the location of a ball. This process can take a few hours to complete, but as it is such an integral part of delivering an accurate system, it is obviously carefully carried out. Once the calibration process has been finished, the system can finally be used to accurately track the ball.
To ensure that nothing has slipped through the system set up, we will perform internal testing as well as very rigorous testing with the ITF, who use a high-speed (1000 fps) camera to verify our results. To test the system, the ITF will use an air-cannon to fire balls down at the court, something you do not want to be on the receiving end of! Once the ITF is happy that our system is tracking accurately by utilising their high-speed camera footage, the system is passed for use at the event.
I’m currently at Wimbledon but have also got upcoming tournaments at the Olympics and in the USA over the summer, leading up to the US Open. I hope to provide you with some feedback on some of these events in the future. Thanks for reading my blog, please feel free to comment and ask questions which I will do my best to answer.