The number of surveillance cameras on our streets has increased dramatically over the past decade. It is difficult to walk longer than a few metres in most cities without seeing another camera. Our movements are monitored constantly.How does surveillance differ from one city or the next? What is the best surveillance camera coverage?Thanks to Hao Sheng's work and the collaboration of colleagues at Stanford University, California, we now have an answer. This group counted the number cameras visible in Google Street View images from 10 US cities and 6 other large cities worldwide.These results show that Seoul, South Korea's capital, has the highest concentration of surveillance cameras, with Boston in the US at the top. These results show that neighborhoods with more non-white residents in the US are more closely monitored.Street SurveillanceGoogle's Street View service was used by the team to gather 360-degree photos of streets and neighborhoods. It has been in use since 2007. Google claims that its Street View cars have traveled more than 10,000,000 miles in 83 countries. They take images of the roads and houses, as well as shops, buildings, along with photos of streets. These images also include visible surveillance cameras.It is difficult for humans to search through such a large database. So Sheng and his colleagues developed a machine vision algorithm that could spot cameras in randomly selected images taken from 16 cities. This allowed for the detection of the density of cameras along roads and the variations in this between areas. These figures were then used by the team to estimate the total number of cameras within the city.Seoul, with nearly one camera per kilometer, is the city with the highest density. The next cities are New York City, Boston, New York City, and Baltimore. Los Angeles, Seattle, and Singapore are at the opposite end of the spectrum. LA has 0.16 cameras per km. Our analysis of U.S. cities also showed that cameras are more common in mixed, industrial and commercial zones than they are in residential areas.There was also a clear trend among non-white neighborhoods in the US. Sheng and her colleagues found a higher concentration of cameras in neighborhoods that are majority-minority. This highlights the need to be mindful of the possible disparate effects of surveillance technology on communities.There are some limitations to the survey. Sheng and co. claim that the method does not capture cameras that are hidden, intentionally hidden, or too small to be seen (e.g. doorbell cameras). The numbers that they found are likely to be lower than the limit. If Google makes them available, higher resolution images could increase the count.Ring of SteelThere is at least one surprise in the results. London, which has been long considered the CCTV capital, is mid-table with 0.45 cameras per km. It's not surprising, considering that London's financial district, also known as the City of London has been well-known for its CCTV surveillance, which was established in the 1990s following a series of terrorist bombing attacks.The Ring of Steel is a system that operates cameras at all entrances and exits to the city. There are also many cameras within the cordon. All images are sent to a central control center that pioneered face recognition and number plates. Many business establishments in the city have their own video surveillance.The 0.45 cameras per km seems a little low considering that London's City is only one square mile. However, other cities have clearly caught up since they were all measured in the exact same way.Next time you go for a walk in the city, smile. You are probably watching TV.Ref: Surveillance Surveillance: Estimating Street View Data to Determine the Prevalence Of Surveillance Cameras: arxiv.org/abs/2105.01764
