Chinese authorities have begun deploying a new surveillance tool called "gait recognition" software that uses people's body shapes and how they walk to identify them, even when their faces are hidden from cameras.

Key points: Software developer Watrix says its program can identify people from 50 metres away

Software developer Watrix says its program can identify people from 50 metres away Gait recognition is being envisioned as a surveillance tool alongside facial recognition

Gait recognition is being envisioned as a surveillance tool alongside facial recognition The technology has been researched for over a decade in Japan, the UK and US

Already used by police on the streets of Beijing and Shanghai, "gait recognition" is part of a push across China to develop artificial intelligence and data-driven surveillance that is raising concerns about how far the technology will go.

The software, built by a Chinese artificial intelligence company called Watrix, extracts a person's silhouette from video and analyses the silhouette's movement to create a model of the way the person walks.

It doesn't require special cameras — the software can use footage from surveillance cameras to analyse gait.

Watrix chief executive officer Huang Yongzhen said its system can identify people from up to 50 metres away, even with their back turned or face covered.

"You don't need people's cooperation for us to be able to recognise their identity," Mr Huang said.

"Gait analysis can't be fooled by simply limping, walking with splayed feet or hunching over, because we're analysing all the features of an entire body."

Watrix employees demonstrate their firm's gait recognition software at their company's offices in Beijing. ( AP: Mark Schiefelbein )

The technology isn't capable of identifying people in real-time yet.

Users instead must upload video into the program, which takes about 10 minutes to search through an hour of video.

Mr Huang envisioned gait recognition being used alongside face-scanning software, which needs close-up, high-resolution images of a person's face to work.

'An unstoppable trend'

Sorry, this video has expired Surveillance software identifies details about people and vehicles in Beijing.(Photo: Reuters/Thomas Peter)

Chinese police are using facial recognition to identify people in crowds and nab jaywalkers, and are developing an integrated national system of surveillance camera data.

Mr Huang is a former researcher who said he left academia after seeing how promising the technology had become.

He then co-founded Watrix in 2016, and his company was incubated by the Chinese Academy of Sciences.

Though the software isn't as good as facial recognition, Mr Huang said its 94 per cent accuracy rate is good enough for commercial use.

A photo is snapped as soon as a pedestrian starts jaywalking. Three more photos will be taken as she crosses the street and comes closer to the camera. ( Supplied: Shenzhen Traffic Police )

But not everyone is comfortable with gait recognition's use.

Security officials in China's far-western province of Xinjiang, a region whose Muslim population is already subject to intense surveillance and control, have expressed interest in the software.

Shi Shusi, a Chinese columnist and commentator, said it was unsurprising the technology was catching on in China faster than the rest of the world because of Beijing's emphasis on social control.

"Using biometric recognition to maintain social stability and manage society is an unstoppable trend," he said.

"It's great business."

Not a new technology

Sorry, this video has expired The Australian Government is using Chinese CCTV cameras, which have been banned by the US Government.

Beyond surveillance, Mr Huang said gait recognition could also be used to spot people in distress, such as elderly individuals who have fallen down.

Mark Nixon, a leading expert on gait recognition at the University of Southampton in Britain, said the technology could make life safer and more convenient.

"People still don't recognise they can be recognised by their gait, whereas everybody knows you can be recognised by your face," Mr Nixon said.

"We believe you are totally unique in the way you walk."

But the technology isn't new.

Scientists in Japan, the United Kingdom and the US Defence Information Systems Agency have been researching gait recognition for over a decade, trying different ways to overcome scepticism that people could be recognised by the way they walk.

Professors from Osaka University have worked with Japan's National Police Agency to use gait recognition software on a pilot basis since 2013.

But few have tried to commercialise gait recognition.

A Watrix employee works at his desk in their company's offices in Beijing. ( AP: Mark Schiefelbein )

Israel-based FST Biometrics shut down earlier this year amid company infighting after encountering technical difficulties with its products, according to former advisory board member Gabriel Tal.

"It's more complex than other biometrics, computationally," Mr Nixon said.

"It takes bigger computers to do gait because you need a sequence of images, rather than a single image."

According to Chinese media, Watrix announced last month that it had raised 100 million yuan ($20 million) to accelerate the development and sale of its gait recognition technology.

AP