Engineers at Vanderbilt University’s Institute for Software Integrated Systems (ISIS) have developed a system that can give soldiers just such an edge by turning their combat helmets into “smart nodes” in a wireless sensor network. Soldiers can carry personal digital assistants that can display the location of enemy shooters in three dimensions and accurately identify the caliber and type of weapons they are firing. (H/T Rocky Rawstern)
An entire node for the ISIS system weighs only slightly more than the four AA batteries that power it and costs about $1,000 to construct using currently available commercial hardware. The range is typically within a few meters even from as far as 300 meters. The more sensors that pick up the shot, the more accurate the localization. “Because the microphones on the helmet are so close together, the precision is not very high,” Ledeczi says. “However, the nodes are continuously exchanging the times and angles of arrival for these acoustic signals, along with their own locations and orientations. When two or more nodes detect the shot, they can provide the bearing with better than one degree accuracy.
ISIS system combines information from a number of nodes to triangulate on shooter positions and improve the accuracy of its location identification process. It also uses a patented technique to filter out the echoes that can throw off other acoustic detection systems.
The ISIS system communicates its findings with the personal digital assistants that the soldiers carry. The PDAs are loaded with maps or overhead pictures of the area upon which the shooter locations are displayed.
In 2006, a team from the National Institute of Standards and Technology at the U.S. Army Aberdeen Test Center independently determined the accuracy of the system. Firing positions were located at distances of 50 to 300 meters from a 10-node sensor network. Six different weapons were used. The only shots that the system sometimes failed to track accurately were those that passed to one side of all of the nodes.
The field tests demonstrated that the system can pick out the location of high-powered sniper rifles even when they are firing at the same time as a submachine gun like the AK-47. They also proved that it can identify the window that a rifle is firing through even when the rifle is completely inside the building, the technique preferred by trained snipers.
Standard GPS locations are inadequate for this purpose and satellite coverage can be spotty in urban environments. The ISIS team has recently solved this problem by adding an inexpensive radio chip that allows them to track the relative position of nodes using high-precision radio interferometry.