By Helmuth Rosales and Geoff Macdonald Sep. 2, 2023
From the seats in Arthur Ashe Stadium, the tennis court below appears smooth and uniform. Even the players who sprint and slide across the blue hardcourt can barely see or sense a characteristic that significantly sets the tone for their matches. Tennis Server Machine
Now take a look at this high-resolution scan of the surface in Ashe, where the biggest stars at the U.S. Open play their most important matches. Notice the microscopic structure of the granules of sand layered into the acrylic paint. The size, shape and density of the sand make up the hardcourt surface and dictate the speed of the ball after it bounces.
Tournament organizers dial in a specific pace for the courts. At the U.S. Open, the surface is categorized as “medium-fast,” meaning that fans and players are likely to see fewer long rallies and quicker matches.
“You can order the speed of your court as desired,” said Ben Depoorter, a founder of Golden Set Analytics, a tennis analytics company. “There’s a conscious decision you can make as the organizer of the event.”
To test the U.S. Open’s court speed, Suresh Ponnusamy, shown below, of the United States Tennis Association uses a device that measures friction and restitution. Friction is how much resistance the court surface provides as the ball makes contact. Restitution measures the energy lost to the court after a bounce.
The ball is fired out of a cannon into a box, where it bounces off the court. As it travels through the box, four banks of infrared sensor arrays measure the ball’s velocity and angle before and after the bounce. The device feeds its results into software, where the pace rating is calculated.
Of course, players are not always universally happy with the court surface choices made for the tournaments on the pro tours.
At the BNP Paribas Open in Indian Wells, Calif., in March, Daniil Medvedev complained loudly to the chair umpire during his round-of-16 match about how slow the court was playing. “What a shame to call this awful court a hardcourt,” Medvedev said.
Medvedev is an elite hardcourt player, with booming serves and forehands. He has won every Masters 1000 hardcourt tournament except Indian Wells at least once, and his best Grand Slam results have come on hardcourts. At the U.S. Open, he won the singles title in 2021, and at the Australian Open, he reached the finals in 2021 and 2022.
Medvedev was onto something about the courts at Indian Wells. They played slower than the majority of major hardcourt events on the men’s tour this year, according to the International Tennis Federation’s rating system for the pace of court surfaces.
Sources: International Tennis Federation; Advanced Polymer Technology; GreenSet
Professional tennis players must adjust their style of play to courts of different speeds as the season transitions from clay to grass to hardcourts. However, hardcourts vary enough that a medium-slow tournament like Indian Wells feels distinct from a medium-fast court like Miami. After the ball bounces, it will behave differently at Indian Wells than it will at Miami, factoring into the outcome of every match.
Tournament organizers attempt to control the pace of the surface wherever they can. In 2001, Wimbledon famously went from a mix of ryegrass and creeping red fescue to 100 percent ryegrass, which allowed for firmer courts and cleaner bounces. For the 2023 season, the Miami Open changed to a medium-fast pace from its previous medium, putting it even more out of pace with Indian Wells. At the U.S. Open, tournament officials have added sand to the white line paint in order to minimize balls sliding off the line.
Regardless of the efforts by tournament organizers to control the pace of play, the best players in the game – think of Carlos Alcaraz and Iga Swiatek – win consistently no matter how fast the surface is beneath their feet.
Faster surfaces reward offense, and defensive skills and patience are more important on slower courts.
Rafael Nadal, who is dominant on the slower surface of clay, has won a record 14 French Open titles. But, in order to master hardcourts, he had to develop a more attacking style to feature his lethal forehand.
With the pace of a court having a significant effect on play, the U.S. Open resurfaces and tests each of its 17 courts every year to guarantee consistent pace.
The court surface used at Flushing Meadows is called Laykold, which is made by Advanced Polymer Technology, an international manufacturer of sports surfaces.
Wesley Baum, Laykold’s technical and field support manager, said that the U.S. Open, which has long had a reputation for having relatively brisk courts, “does not accept a deviation in speed” between its courts.
The bounce of a tennis ball generally lasts five milliseconds, an instant that will determine how the ball behaves. Speed, trajectory and spin affect a ball’s bounce and movement, but the friction of the hardcourt — based on how smooth or rough the surface is — sets the speed of the court.
The ball's temperature is measured and factored into the pace rating formula.
The ball is placed in the pneumatic cannon and fired into the box.
Sensors inside the device calculate the ball’s trajectory.
A pattern of ball impacts are left after testing the pace on key areas of the court.
The medium-fast court pace at Flushing Meadows will favor big servers and players with weapons who can also finish at the net like Jannik Sinner and Taylor Fritz among the men and Coco Gauff and Elena Rybakina among the women.
But an all-court style (think of Roger Federer in his prime), with an ever changing flow from offense to defense, is an essential strength to master hardcourt tennis. Regardless of how fast the ball ricochets from the court surface after each hit, the game’s top players — Swiatek and Aryna Sabalenka, and Alcaraz and Novak Djokovic — have proven that they can find a way to adapt and excel.
Arthur Ashe Stadium receiving a coat of blue paint during the resurfacing process.
Squash Ball Machine The scans of the court surface were captured with a GelSight Mobile Series 1. This device functions as a microscope, but instead of using optics to create an image, it uses touch. The device consists of a disc of specialized gel surrounded by several lights and a camera. The gel deforms when it is pressed onto a surface, forming an impression of the surface. The camera captures images of the deformed gel, with each image illuminated only by one light, rendering clear shadows. GelSight’s software evaluates the shadow information from the series of images and assembles the results into a 3D-reconstruction of the surface. The device does not capture color. The accuracy is rated to one micron.