Cricket, tennis and now football use Hawk-Eye - but how accurate is it?

Hawk-Eye's technology is an impressive tool that makes the lives of referees and umpires easier, but don't be fooled - there's a chance that Hawk-Eye could sometimes get a call wrong.

Hawk-Eye is a device used to reconstruct the track of the ball for LBW decisions in cricket and for line calls in tennis. It will be much in evidence during the remaining Ashes tests and is now being used for goal-line decisions in Premier League football. The technology is at its best when officials make a really bad decision.

But there are things you might not know about Hawk-Eye. For instance, it cannot track the ball to a millimetre even though one might get this impression when watching some replays; in tennis, those shots shown to be touching the line by a hair’s breadth and called in might actually be out and vice-versa.

Few people realised that there was an issue with accuracy until my colleagues and I wrote about it in 2008; even top scientists were quite surprised until they thought about it.

How it works
Reconstructed track-devices such as Hawk-Eye work by using a number of TV cameras to record the position of the ball in each frame, then a computer reconstructs the path and projects it forward from the last frame.

These devices were first used to aid leg-before-wicket decisions in cricket. The projection-forward principle is the same in tennis since it is unlikely that a camera shutter will be open at the exact moment the ball hits the ground next to the line so the crucial position has to be estimated from a series of previous positions.

What we uncovered
From the frame-rate of the cameras and the speed of the ball, a back-of-an envelope calculation gave the range of possible accuracy and it turned out to be less than the replays suggested. So we telephoned the firm to talk about it and we hit a wall. As sociologists of science we had spent decades chatting with scientists about this kind of thing but suddenly we were told this information was private and lawyers were on call. Before we could publish our first paper we had to ask Cardiff University to back us in case we were hauled into court.

Our results were based on the range of possibilities for frame-rate and such other technical matters we could glean from the internet but detailed data for these devices was and still is secret. The International Tennis Federation refuses to release the details of its tests and the International Cricket Council also keeps its results under wraps. I have tried and tried to get the information from them and the scientists they commissioned to do the testing but am always met with the claim that the information is commercially sensitive.

Margin of error
The problem with reconstructed track devices is that their output is based on estimates. The position of the ball in any one frame is a blob of pixels. The future path of the ball must be extrapolated from at least three frames if the ball is swerving but if it is moving fast and the bounce point is near to the crucial impact point there may not be three frames.

Even with three frames, projections have errors and if, as in tennis, the ball distorts on impact, the footprint on which the line call is based is, again, the result of an inexact calculation – and so on. Hawk-Eye itself used to claim an average error of 3.6 millimetres; more recently it claims this has been improved to average of 2.2mms. However, particularly in tennis, the reliance on this technology to provide a definitive call means that this margin of error isn’t reflected in the replays, leading most fans to assume it is 100 percent accurate.

Accuracy, of course, will depend on the speed and the angle of the ball and many other factors which is why these are average figures and, as with all averages, on occasion the error will be bigger – sometimes much bigger. To know what is going on one needs details of the tests and the distribution of errors that resulted.

Tech and circuses
Assuming that tennis and football lovers, unlike enthusiasts for, say, the professional wrestling circus, want to see fairness as well as an entertaining spectacle, they ought to know more about how the technology is trying to work out what happened to the ball.

When the ball is really close to the line we should see something like a spinning coin to indicate that the final judgement has a lot of chance in it. The crowd would still get its decision and fun but something closer to the truth would be on display.

More and more, computers are able to simulate what looks like reality and this is dangerous for the future of society. The public needs to learn to question technological claims such as those that have been made for anti-missile weapons systems. In certain sports some spectators think that technology is infallible when it is not.

Paul Hawkins, the founder of the Hawk-Eye company, recently said our arguments were “typical of people who spent a lot of time in universities rather than on the tennis circuit”. He’s right, and thank goodness for that.

Harry Collins does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.The Conversation

This article was originally published at The Conversation. Read the original article.

 

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Andy Murray reacting to a Hawk-Eye call at Wimbledon, 2013. (Photo: Getty)
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Who will win in Copeland? The Labour heartland hangs in the balance

The knife-edge by-election could end 82 years of Labour rule on the West Cumbrian coast.

Fine, relentless drizzle shrouds Whitehaven, a harbour town exposed on the outer edge of Copeland, West Cumbria. It is the most populous part of the coastal north-western constituency, which takes in everything from this old fishing port to Sellafield nuclear power station to England’s tallest mountain Scafell Pike. Sprawling and remote, it protrudes from the heart of the Lake District out into the Irish Sea.

Billy, a 72-year-old Whitehaven resident, is out for a morning walk along the marina with two friends, his woolly-hatted head held high against the whipping rain. He worked down the pit at the Haig Colliery for 27 years until it closed, and now works at Sellafield on contract, where he’s been since the age of 42.

“Whatever happens, a change has got to happen,” he says, hands stuffed into the pockets of his thick fleece. “If I do vote, the Bootle lass talks well for the Tories. They’re the favourites. If me mam heard me saying this now, she’d have battered us!” he laughs. “We were a big Labour family. But their vote has gone. Jeremy Corbyn – what is he?”

The Conservatives have their sights on traditional Labour voters like Billy, who have been returning Labour MPs for 82 years, to make the first government gain in a by-election since 1982.

Copeland has become increasingly marginal, held with just 2,564 votes by former frontbencher Jamie Reed, who resigned from Parliament last December to take a job at the nuclear plant. He triggered a by-election now regarded by all sides as too close to call. “I wouldn’t put a penny on it,” is how one local activist sums up the mood.

There are 10,000 people employed at the Sellafield site, and 21,000 jobs are promised for nearby Moorside – a project to build Europe’s largest nuclear power station now thrown into doubt, with Japanese company Toshiba likely to pull out.

Tories believe Jeremy Corbyn’s stance on nuclear power (he limply conceded it could be part of the “energy mix” recently, but his long prevarication betrayed his scepticism) and opposition to Trident, which is hosted in the neighbouring constituency of Barrow-in-Furness, could put off local employees who usually stick to Labour.

But it’s not that simple. The constituency may rely on nuclear for jobs, but I found a notable lack of affection for the industry. While most see the employment benefits, there is less enthusiasm for Sellafield being part of their home’s identity – particularly in Whitehaven, which houses the majority of employees in the constituency. Also, unions representing Sellafield workers have been in a dispute for months with ministers over pension cut plans.

“I worked at Sellafield for 30 years, and I’m against it,” growls Fred, Billy’s friend, a retiree of the same age who also used to work at the colliery. “Can you see nuclear power as safer than coal?” he asks, wild wiry eyebrows raised. “I’m a pit man; there was just nowhere else to work [when the colliery closed]. The pension scheme used to be second-to-none, now they’re trying to cut it, changing the terms.”

Derek Bone, a 51-year-old who has been a storeman at the plant for 15 years, is equally unconvinced. I meet him walking his dog along the seafront. “This county, Cumbria, Copeland, has always been a nuclear area – whether we like it or don’t,” he says, over the impatient barks of his Yorkshire terrier Milo. “But people say it’s only to do with Copeland. It ain’t. It employs a lot of people in the UK, outside the county – then they’re spending the money back where they’re from, not here.”

Such views might be just enough of a buffer against the damage caused by Corbyn’s nuclear reluctance. But the problem for Labour is that neither Fred nor Derek are particularly bothered about the result. While awareness of the by-election is high, many tell me that they won’t be voting this time. “Jeremy Corbyn says he’s against it [nuclear], now he’s not, and he could change his mind – I don’t believe any of them,” says Malcolm Campbell, a 55-year-old lorry driver who is part of the nuclear supply chain.

Also worrying for Labour is the deprivation in Copeland. Everyone I speak to complains about poor infrastructure, shoddy roads, derelict buildings, and lack of investment. This could punish the party that has been in power locally for so long.

The Tory candidate Trudy Harrison, who grew up in the coastal village of Seascale and now lives in Bootle, at the southern end of the constituency, claims local Labour rule has been ineffective. “We’re isolated, we’re remote, we’ve been forgotten and ignored by Labour for far too long,” she says.

I meet her in the town of Millom, at the southern tip of the constituency – the opposite end to Whitehaven. It centres on a small market square dominated by a smart 19th-century town hall with a mint-green domed clock tower. This is good Tory door-knocking territory; Millom has a Conservative-led town council.

While Harrison’s Labour opponents are relying on their legacy vote to turn out, Harrison is hoping that the same people think it’s time for a change, and can be combined with the existing Tory vote in places like Millom. “After 82 years of Labour rule, this is a huge ask,” she admits.

Another challenge for Harrison is the threat to services at Whitehaven’s West Cumberland Hospital. It has been proposed for a downgrade, which would mean those seeking urgent care – including children, stroke sufferers, and those in need of major trauma treatment and maternity care beyond midwifery – would have to travel the 40-mile journey to Carlisle on the notoriously bad A595 road.

Labour is blaming this on Conservative cuts to health spending, and indeed, Theresa May dodged calls to rescue the hospital in her campaign visit last week. “The Lady’s Not For Talking,” was one local paper front page. It also helps that Labour’s candidate, Gillian Troughton, is a St John Ambulance driver, who has driven the dangerous journey on a blue light.

“Seeing the health service having services taken away in the name of centralisation and saving money is just heart-breaking,” she tells me. “People are genuinely frightened . . . If we have a Tory MP, that essentially gives them the green light to say ‘this is OK’.”

But Harrison believes she would be best-placed to reverse the hospital downgrade. “[I] will have the ear of government,” she insists. “I stand the very best chance of making sure we save those essential services.”

Voters are concerned about the hospital, but divided on the idea that a Tory MP would have more power to save it.

“What the Conservatives are doing with the hospitals is disgusting,” a 44-year-old carer from Copeland’s second most-populated town of Egremont tells me. Her partner, Shaun Grant, who works as a labourer, agrees. “You have to travel to Carlisle – it could take one hour 40 minutes; the road is unpredictable.” They will both vote Labour.

Ken, a Conservative voter, counters: “People will lose their lives over it – we need someone in the circle, who can influence the government, to change it. I think the government would reward us for voting Tory.”

Fog engulfs the jagged coastline and rolling hills of Copeland as the sun begins to set on Sunday evening. But for most voters and campaigners here, the dense grey horizon is far clearer than what the result will be after going to the polls on Thursday.

Anoosh Chakelian is senior writer at the New Statesman.