So when Clark found the new generation of road sensor, Arnu drove out to help investigate further. The pair found that, at close range, they could use a handheld frequency counter to pick up the wireless signals given off by the devices as a car passes. Over the following month and half, Clark and Arnu engaged in a kind of geocaching game with the Men in Black, systematically sniffing out the road sensors with the frequency counter, exhuming them, and opening them up. They discovered that each device was coded with three-digit identifier that could be read off an internal dial, allowing Arnu to make a list that correlated each unit's ID number with its GPS coordinates, creating a virtual map of a portion of the surveillance network surrounding the Groom Lake facility. Some of the sensors were miles away from the base.

"We dug up about 30 or 40 of them on various access roads leading to the base on public land," Arnu says, insisting that he and Clark always carefully reburied each unit after logging it, and even tested it with the frequency counter to make sure it was still working before moving on to the next one.