Around the world, about a billion people live in improvised settlements, such as Brazil's favelas, which are often too chaotic to be mapped using satellite imagery or other conventional methods. Being unplanned, these neighbourhoods lack many basic services. Living conditions tend to be unhealthy, and life expectancies lower than national averages.
Rocinha, in Rio de Janeiro, is one of Brazil's largest favelas, where more than 100,000 people live in an area of just 1.5 square kilometres. Scientists from the MIT Senseable City Lab, in the US, have mapped Rocinha with handheld 3D scanners that use LiDAR ("light detection and ranging"). This technology works by projecting infrared light and measuring how long it takes for the light to bounce off an object.
In this way, the scientists have created a virtual 3D model of the area. This will allow better access to services, like waste collection, and improve living conditions, by enabling changes to house construction, for example, that can let in more air and light.