While in the challenging world of competitive sport there is no substitute for natural talent, the high-end equipment used by today’s top players definitely has a positive impact on the game they play. Whether it’s the powerful capabilities of the latest titanium racket frame, the perfectly machined balls or the intricately woven Vectran strings used for maximum shot placement, all kit is aimed at improving a player’s game.
However, state-of-the-art tennis technology doesn’t start and end with the player. How tennis is watched, adjudicated and competed is also evolving thanks to a plethora of advanced systems and inventions, from the omniscient Hawk-Eye ball-tracking system to the awesome data-gathering capabilities of court information computers.
Excitingly, much of this technology is now filtering down to a commercial level, allowing tennis amateurs across the globe to augment their game. So read on to see how just a few additions to your kit bag may help transform you from a novice to a Nadal…
Line calls in major tennis tournaments are now computerised, delivered by the highly advanced Hawk-Eye tracking system. Hawk-Eye uses five or six high frame-rate cameras to capture the exact 3D position of the centre of a tennis ball, recordind the action at a rate of 60 frames per second (fps), twice the speed of a standard TV. Computers capture time-lapsed images taken by the cameras from all directions to map the trajectory of the ball, calculating data a rate of 1 billion equations per rally. Virtual reality software turns these calculations into a graphics that viewers can see and understand.
The system works in a four-stage process. Firstly, vision processing is used to identify the centre of the ball within each frame of multiple cameras. Camera movement is compensated for by also tracking the lines of the court. Secondly, the Hawk-Eye system triangulates the information from each calibrated camera to provide the 3D position of the ball. Thirdly, the triangulation process is repeated for each frame of the replay, generating a 3D trajectory for the travelling ball. Finally, computers determine the amount of compression the ball will undergo as it touches the ground, giving a bounce mark wider than the ball with an accuracy of 2-3mm. The process takes less than a second, meaning quick calls can be made in tennis on whether a ball has bounced inside a line or not. All of this is used to deduce if the ball landed within the boundaries of the court or not, and presented with a visual representation to the officials and public.
Hitting the ball
The materials used to construct the frame determine the racket’s weight, which helps define its power and handling characteristics. Light rackets are easier to handle, but they offer less power.
String pattern and construction materials vary. Tight patterns allow for greater control and ball spin levels. However, wide patterns offer more string flex and therefore more elasticity and power.
Grips come in various sizes and are made from differing materials. Larger grips allow better purchase and stability, while thinner ones offer manoeuverability.
When the tennis ball is struck it deforms under pressure. Its pressurised rubber core, however, absorbs energy and returns it on expansion, causing the ball to spring off the racket’s strings.
Modern tennis rackets are made from metals such as titanium and aluminium, as well as materials including graphite, ceramics, glass fibre and boron, to create a composite frame. Unlike tennis balls, racket design shape, length and weight are not standardised, and vary from player to player. For example, lengths range between 53cm (21 inches) and 70cm (27.5 inches) dependent on the size/preference of the user, while weights tend to vary from 230g (8oz) to 350g (12oz) unstrung.
Racket strings are made from natural and man-made materials, from cow intestine through to nylon and polyester and on to kevlar and vectran. Each string type delivers different qualities – stiffness, rebound efficiency, etc – and is selected by players to complement their own strengths. Racket string patterns also vary, with looser strings granting more power, tighter patterns and more control. The Six.One Tour BLX racket from Wilson is a great example of a modern, composite racket.
Top power is achieved by using materials that keep the racket stiff.
Leather grips offer better moisture absorption, comfort and control.
Modern nylon can replicate the effect of natural gut.
Modern tennis balls are made from a hollow rubber core, covered in a wool/nylon shell. Air inside the core is pressurised granting the ball its bounce; the shell is affixed by a heated press, leaving the white manufacturing seams visible. Finished balls must measure 6.35cm (2.5 in) in diameter and weigh 56.7g (2oz). Rules regarding bounce must be adhered to, with any ball not bouncing between 53 to 58 inches when dropped from 100 inches seen as unusable. To keep them in top condition, spare balls are kept at the side of the court in a refrigerated container at 68°F. For Wimbledon 2011, Slazenger is providing an anniversary edition of its Ultra Vis Hydroguard balls.
Televised coverage and commentary for Wimbledon 2011 is distributed by the BBC worldwide, which has 90 cameras – both robotic and manual – positioned around the complex. Information is drawn from the Wimbledon information system (WIS), an IBM-designed multimedia computing system that tracks and provides data on draws, order of play, point-by-point scores, biographies and statistics (such as forehand/backhand winners, aces, direction, speed of serve and unforced errors). The WIS system gathers its information from sensors such as the IBM radar gun, a machine positioned behind the baseline at both ends of the court that records ball speed. Lenovo ThinkPad laptops are also positioned at the side of each court and linked directly to the WIS central server, into which statistics are manually inputted.
Clay courts are made from crushed brick and stone and offer the slowest tennis surface available, slowing the ball due to its greater impact resistance. Clay also reduces the impact on players themselves, with individuals capable of sliding into shots due to the loose surface and consequently conserving energy. Lastly, balls bounce higher on clay than on grass and with greater consistency.
And then there are hard courts, which are made out of asphalt or concrete. These offer a middle ground between clay and grass, delivering a moderately fast surface that is faster than the former, but slower than the latter.
Still feel like you don’t quite know enough to take on Murray, Nadal and co? Well then, make sure you check out our other tennis-related articles, Controversial Hawk-Eye Moments and Five facts about Wimbledon.