This week, engineers working at the University of California, Santa Barbara have released the results of their research into using drones to see and measure three-dimensional objects through walls. The technology, which uses ordinary wireless signals, is astounding.
“Our proposed approach has enabled unmanned aerial vehicles to image details through walls in 3-D with only Wi-Fi signals,” said Yasmin Mostofi, an engineering professor working on the project. “This approach utilizes only Wi-Fi RSSI measurements, does not require any prior measurements in the area of interest and does not need objects to move to be imaged.”
To experiment with the technology, Mostofi and her team deployed two consumer-grade drones around an enclosed brick structure with an interior inaccessible to the UAVs. The two drones each perform separate tasks, with one of them transmitting a wireless signal and the other constantly measuring the power of that signal. These experiments build on developments made by Mostofi Labs during the past few years.
The team’s imaging technology is able to produce a composite image of the drone’s measurements, which have been close matches to the brick structure’s actual size throughout the experiments completed so far.
Their approach to producing through-wall imagery makes use of four networked components. First, they outline the most efficient paths for the drone to travel while still allowing for complete measurement of the brick structure’s perimeter.
Next, they modeled the structure’s interior as what’s called a “Markov Random Field,” which tells the imaging program that there’s unknown information within the thing it’s rendering. The program uses a graph-based approach to keep track of and measure each “voxel”. Think about this as if every object is made up up tiny cubes, like pixels, and the machine is measuring and compiling each one into a total image. Voxels are those tiny cubes.
Then, a linear wave model is used to make a rough map of the interaction between the Wi-Fi signal and the area inside of the structure.
Finally, the collected information is compressed and less than 4% of the total Wi-Fi signals are compiled to produce a “final” image of the space’s interior.
Amazing!
All images via Mostafi Labs
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