

The Pentagon wants to be able to peer inside your apartment building – picking out where all the major rooms, stairways, and dens of evil-doers are.

The U.S. military is getting better and better at spotting its enemies, when they're roaming around the streets. But once those foes duck into houses, they become a whole lot harder to spot. That's why Darpa, the Defense Department's way-out research arm, is looking to develop a suite of tools for "external sensing deep inside buildings." The ultimate goal of this Harnessing Infrastructure for Building Reconnaissance (HIBR) project: "reverse the adversaries' advantage of urban familiarity and sanctuary and provide U.S. Forces with complete above- and below-ground awareness."

By the end of the project, Darpa wants a set of technologies that can see into a 10-story building with a two-level basement in a "high-density urban block" – and produce a kind of digital blueprint of the place. Using sensors mounted on backpacks, vehicles, or aircraft, the HIBR gear would, hopefully, be able to pick out every room, wall, stairway, and basement in the building – as well as all of the "electrical, plumbing, and installation systems."

Darpa doesn't come out and say it openly. But it appears that the agency wants these HIBR gadgets to be able to track the people inside these buildings, as well. Why else would these sensors be required to "provide real-time updates" once U.S. troops enter the building? Perhaps there's more about the people-spotting tech, in the "classified appendix" to HIBR's request for proposals.

There are already a number of efforts underway, both military and civilian, to try to see inside buildings. The Army has a couple of hand-held gadgets that can spot people *just *on the other side of a wall. Some scientists claim that can even catch human breathing and heartbeats beyond a barrier.

Darpa's Visibuilding program uses a kind of radar to scan structures. The problem isn't sending the radio frequency (RF) energy in. It's "making sense of the data produced from all the reflected signals" that come back, Henry Kenyon wrote in a recent *Signal *magazine article. Besides processing data from the inside a structure, the system also must filter a large amount of RF

propagation in the form of randomly reflected signals. Although radar technologies exist that can track people in adjacent rooms, it is much more difficult to map an entire building. “Going through one wall is not that bad, but a building is basically an RF hall of mirrors. You’ve got signals bouncing all over the place,” Darpa program manager Dr. Edward J. Baranoski says. Field trials are supposed to get underway this fall.