Researchers at UC Santa Barbara demonstrated of three-dimensional imaging of objects through walls using ordinary wireless signal. The technique, which involves two drones, could have a variety of applications, such as emergency search-and-rescue, archaeological discovery and structural monitoring. Led by Prof. Yasamin Mostofi, the team utilized a couple of autonomous octocopter drones, both of which were equipped with Wi-Fi transceivers. As they flew in synchronous paths on either side of a four-sided brick structure, one of them continuously transmitted a Wi-Fi signal, while the other measured the strength of that signal as it was received after passing through the bricks. By analyzing the received signal strength, it was possible to ascertain the size and shape of objects hidden within the structure, as they disrupted some of the signal.
The ground-based robots are able to get 2D images, the drones are able to assess the objects from a wider range of angles, resulting in 3D images. There’s more information in the video below.