Heat seeker

4 min read

Thermal imaging cameras usually found on fighter jets are at the heart of sportscasting’s latest technical innovation. Jon Excell reports.

Whether it’s the PlayerCam that follows individual footballers over the course of a match, or the Hawk-Eye system used to predict the trajectories of cricket, tennis and, most recently, snooker balls, TV sports viewers are frequently the first to be exposed to hi-tech broadcasting innovations.

In a fascinating and unusual tale of technology transfer, the latest broadcasting device to enrich the armchair fan’s viewing experience is based on a system more commonly found on armoured tanks and fighter jets.

Hot Spot, unveiled by Sky Sports during the summer’s first test match between England and the West Indies, uses powerful infrared cameras to detect the distinct thermal signature left when a cricket ball hits a pad, clips the edge or flies off the middle of the bat.

Developed by BBG Sports — the small Australian firm behind the ‘snickometer’ and the speed gun — Hot Spot uses two powerful thermal imaging cameras positioned above the field of play at opposite sides of a ground. These devices, which can be up to 90m away from the action, remotely sense and measure the tiny amount of heat generated by the collision of a cricket ball and then create a black and white negative image which shows the ball’s precise point of contact.

Talking to the Engineer from Headingly ahead of last month’s second test match, BBG’s Warren Brennan explained how the system was developed: ‘We came across the technology about four years ago and thought it was quite interesting. We sat down and thought about whether we could apply it to different sports and cricket is the first one we’ve done.’

Brennan and his team evaluated a number of different systems before settling on the core element of Hot Spot system: a military standard Emerald LR infrared camera manufactured by French imaging specialist CEDIP. ‘We started off with standard hand-held cameras of the type that electrical contractors use to look at electrical circuits, but they didn’t do the job. So we moved up to the next stage and finally got up to the top-end military stuff and started to get better results.’

The key to obtaining these results, said Brennan, was the use of so-called cooled cameras, where the sensitivity of the system is enhanced by an internal cooling system that maintains the infrared sensor at a low temperature. Brennan said that the Hot Spot application makes BBG sports one of the first customers for the cameras outside of the military sphere.

Unsurprisingly, buying military-grade equipment, modifying it, and then lugging it about all over the world is not exactly a straightforward process and BBG had to jump through a number of bureaucratic hoops to get the system off the ground. Indeed, before settling on the CEDIP system, the team was in discussions with a US company that is the only other manufacturer of thermal cameras with a high enough resolution. It was this company’s unwillingness to part with its technology that led Brennan to the French.


Hot Spot remotely senses and measures the tiny amount of heat generated by the collision of a cricket ball and then creates a black and white negative image showing the ball’s precise point of contact

‘The Americans were so protective of their technology I couldn’t even take a camera from the UK to France without having to go through a lengthy process of export licensing and all that sort of rubbish,’ he complained.

CEDIP and the French government, recognising that the technology is being used for nothing more sinister than to enhance the enjoyment of a cricket match, have been more flexible. But although Brennan has not encountered any problems taking the system between Europe and Australia, he said that there could be issues taking Hot Spot into less politically stable cricketing nations such as Pakistan.

Other than a couple of key modifications relating to the connectivity of the camera, Brennan explained that the hardware now being used by Sky is not all that different to the camera that CEDIP sells to the military. Its rugged military design lends the device perfectly to the rigours of major outdoor sporting events. ‘It’s fully waterproof and in a lot of ways is up to broadcast standard. It can sit outside in the rain,’ said Brennan.

With the hardware already in place, BBG’s main role was developing the software that captures and processes the images from both cameras in real time. ‘we took the concept of what comes out of the camera, wrote all the software to process that and built a broadcast interface around that so that we were able to offer the output of the infrared cameras in real-time to TV,’ explained Brennan.

Though most reactions to Hot Spot have been positive, the technology has not been without its critics, and the Sky team has perhaps been guilty of getting a little over-excited with its new toy, using it a bit more frequently than is really necessary.

But Brennan is positive the system really adds something to the coverage. ‘They may over-use it initially, but over time they will find that they use it a little more selectively,’ he said. ‘It provides a different perspective on things. For example, a commentator will say, “well he really hit that one out of the middle of the bat”, and when we go back and replay it you’ll find that it’s near the bottom of the bat. You don’t want to contradict things but people like to see exactly what’s happening.’

Clearly, the system is not necessarily limited to cricket, and the team is currently testing it out on tennis courts where, said Brennan, it has immense promise. ‘we’ve found that when the ball hits the ground it leaves a perfect impression of a ball mark — everyone that we’ve shown it to in the tennis fraternity agree that it’s as accurate as you can possibly get.’

Brennan said he will be working on the development of the tennis system over the next 12 months and hopes that after that it could even ultimately replace the much trumpeted Hawk-Eye — ‘if accuracy is the most important issue, it has the edge on Hawk-Eye. We’ll have to wait and see how our development goes; we’re very happy with the accuracy.’

But despite the system’s undoubted accuracy, Brennan believes that this kind of technology is unlikely to find its way into the hands of cricket match referees and umpires, and is probably, like Hawk-Eye, destined to remain a broadcasting novelty.

‘I’ve worked in the industry for almost 20 years, and I’ve never seen anything to rival sports politics,’ he said. ‘I don’t even think general politics rivals sport because people become so much more passionate about it. My gut feeling is that this stuff won’t be used at an official level.’