Using ordinary Wi-Fi networks
Researchers at The University of California Santa Barbara have developed a system that allows a pair of drones working together to see through walls.
The technique, which uses nothing but standard Wi-Fi signals and off-the-shelf components, was invented by researchers working in the lab of Yasamin Mostofi, a professor of electrical and computer engineering.
“Our proposed approach has enabled unmanned aerial vehicles to image details through walls in 3D with only Wi-Fi signals,” said Mostofi.
“This approach utilizes only Wi-Fi [signal strength] measurements, does not require any prior measurements in the area of interest and does not need objects to move to be imaged.”
You can see the drones in action in the following video:
In tests, the team demonstrated two autonomous octocopters taking off and flying outside an enclosed, four-sided brick house. One copter continuously transmits a Wi-Fi signal, while the other one measures the strength of that signal.
A picture can then be built up of the contents of the house, because the signal is affected by the shapes of the objects within. The result is a high-resolution 3D image of the interior, which closely matched the real thing.
“High-resolution 3D imaging through walls, such as brick walls or concrete walls, is very challenging,” said Chitra R. Karanam, the lead PhD student on the project, “and the main motivation for the proposed approach.”
Mostofi added: “Enabling 3D through-wall imaging of real areas is considerably more challenging due to the considerable increase in the number of unknowns.”