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Mainland China is home to eight of the world’s 10 most heavily monitored cities, according to a recent study by Comparitech*. And the use of closed-circuit television (CCTV) cameras is increasing throughout the world.

Authorities argue cameras reduce crime and increase public safety, but some civil liberty groups say such systems are open to abuse and can be used to monitor political critics. It is increasingly difficult for citizens to protect their privacy in public spaces. This has led San Francisco to become the first American city to ban the police and other law enforcement agencies from using facial recognition technology software. * Comparitech is a British pro-consumer website providing information for research and comparison of tech services The world’s top 10 most surveilled cities City No. of cameras/

1,000 people Crime

index¹ Freedom

score¹ Chongqing 168.03 33.18 11 Shenzhen 159.09 43.29 11 Shanghai 113.46 41.07 11 Tianjin 92.87 29.15 11 Jinan 73.82 15.93 11 London 68.4 52.12 93 Wuhan 60.49 21.18 11 Guangzhou 52.75 47.43 11 Beijing 39.93 42.16 11 Atlanta 15.56 62.64 86 ¹ The values range from 0 to 100. A high crime index number shows high levels of crime while a high freedom score indicates greater civil liberty The top 20 most surveilled cities

It has been widely reported that China has about 200 million CCTV cameras in use, a figure predicted to rise 213 per cent by 2020 to 626 million.

Software recognition accuracy Facial recognition has become a part of daily life in many countries, but nowhere more so than in China. Powered by the rise of cloud computing, machine learning and precise digital cameras, accuracy rates are still based on having an unobstructed view of a person’s face. One of the ways facial recognition works is by measuring features. Some researchers believe the correct identification rate can drop by up to 70 per cent, depending on how much of a face is covered.

Gait recognition Due to the limitations of facial recognition, China has started testing a new technology that it claims can identify people from a distance of 50 metres (164 feet) with up to 94 per cent accuracy. It is based on a person’s walk and it is not easy to fool the system. The system analyses a person’s body shape and body movements as well as their leg movements. Simply disguising your walk won’t fool the data. The system uses segment contours of the human body to compute a gait cycle by analysing the change in width of a body’s silhouette. Sequences of the images are used to calculate a gait energy image.

The top most surveilled cities (21 - 100) Comparitech found a weak correlation between the number of cameras and how safe they made people feel. Hover/tap for information

Hong Kong’s public surveillance The city is estimated to have at least 50,000 CCTV cameras.