Through-the-Wall Surveillance Technologies

Article excerpt

Authors' Note: The views and opinions in this article are those of the authors and do not necessarily reflect those of the US. government. References to any specific commercial products by trade name, trademark, manufacturer or otherwise do not necessarily constitute or imply its endorsement, recommendation or favoring by the U.S. government.

Inmates have barricaded hostages in a room without surveillance access. You do not know where or how many inmates or hostages there are. You do not know if they are armed or if correctional officers will be in harm's way if they are sent in. This is one of the worst situations corrections professionals face because unknown information could cost lives. But what if you could "see" through the walls?

Each year correctional and law enforcement officers are injured because they lack the ability to detect and track offenders through building walls. The National Institute of Justice's Office of Science and Technology (OS&T) has a comprehensive program to help solve that problem and has made the development of through-thewall surveillance (TWS) technologies a top priority. The technology projects that comprise the program are divided into two broad categories: relatively inexpensive, handheld devices that alert officers to the presence of an individual behind a wall or door; and portable, personal computer-based devices that will enable Special Weapons and Tactics (SWAT) or Special Operations Response Team (SORT) team commanders to better visualize events during hostage situations.

Simple to Complex

OS&T has concentrated on developing low-power, radar-based devices that do not pose health risks to users or the public. Those devices do not provide pictures; they do not work like a television. The handheld devices simply provide a blinking light or modulating sound that indicate movement behind a wall or door. That movement may be as slight as the breathing motion of an individual's chest.

The Georgia Tech Research Institute (GTRI) is developing an inexpensive, handheld radar device that will detect individuals through interior walls and doors. A laboratory model of the Radar Flashlight was able to detect an individual through sections of home siding and drywall, a wooden front door and a section of brick and mortar.

Portable PC-based TWS devices are more capable but more expensive than handheld devices. The handheld devices should be available for a few hundred dollars, the portable devices will probably sell for several thousand dollars. With extra money, an agency will purchase added capabilities ranging from providing the direction and distance to individuals moving in a building, to providing an outline of a room and the location of individuals on a computer screen. In addition to indicating interior walls, such devices also may be able to indicate large pieces of furniture, as well as where individuals are located within a building or room.

Raytheon (formerly Hughes Missile Systems) is developing a portable, briefcase-size device for SWAT applications. This device, the Motion and Ranging Sensor (MARS), is a modification of a commercial motion detector sold by Hughes Missile Systems. It employs a radar that can locate and track an individual through reinforced concrete or brick walls.

"Sorting Out"

Researchers also are exploring ways to sort the "good guys" from the "bad guys." SWAT and SORT team members can be targeted with markers that send back a unique signal to the radar source -- in this case the TWS device. The unique signal positively identifies the team member as a good guy. Additionally, in a corrections environment, all staff and other appropriate personnel could be covertly tagged, as could be VIPs in a non-corrections environment. OS&T entered into discussions with British Aerospace (formerly the Sanders division of Lockheed-Martin Sanders (LMS)) to assess the utility of a passive tagging technology for TWS application. …