Researchers at the University of California, Santa Barbara (UCSB) working out of professor Yasamin Mostofi’s lab have conducted a demonstration in which they used two UAS working in tandem, and WiFi, to capture the three-dimensional imaging of objects through walls.

In their experiment, which the results of that and the proposed methodology appeared in the Association for Computing Machinery/Institute of Electrical and Electronics Engineers International Conference on Information Processing in Sensor Networks (IPSN), researchers use two autonomous octocopters to fly outside of an enclosed, four-sided brick house whose interior is foreign to the UAS.

According to the researchers, “one copter continuously transmits a WiFi signal, the received power of which is measured by the other copter for the purpose of 3D imaging.”

After traveling a few proposed routes, the UAS use imaging methodology developed by the researchers to not only reveal the area behind the walls, but also to generate 3D high-resolution images of the objects inside.

The researchers say that the 3D image closely matches the actual area.

“This approach utilizes only WiFi RSSI measurements, does not require any prior measurements in the area of interest and does not need objects to move to be imaged,” Mostofi says through an article with the UC Santa Barbara school website.

Four tightly integrated key components are the heart of the researchers’ strategy to enable 3D through-wall imaging. To start, they proposed robotic paths that can “capture the spatial variations in all the three dimensions as much as possible, while maintaining the efficiency of the operation.”

Second, to capture the spatial dependencies, the researchers molded the three-dimensional unknown area of interest as a Markov Random Field, and used a graph-based belief propagation approach “to update the imaging decision of each voxel (the smallest unit of a 3D image) based on the decisions of the neighboring voxels.”

Third, the researchers used a linear wave model to “approximate the interaction of the transmitted wave with the area of interest.”

Lastly, the researchers “took advantage of the compressibility of the information content to image the area with a very small number of WiFi measurements.”

Being able to use UAS and WiFi for 3D through-wall imaging could have a variety of use cases, including for structural monitoring, archaeological discovery, and search and rescue missions.