The Global Positioning System (GPS) has proved a boon for those with a bad sense of direction, but the satellite-based system isn’t without its shortcomings. Something as simple as going indoors or entering a tunnel can render the system useless. That might be inconvenient for civilians, but it's potentially disastrous for military users for whom the system was originally built. DARPA is addressing such concerns with the development of a self-sufficient navigation system that can aid navigation when GPS is temporarily unavailable.
We’ve looked at numerous approaches using various mixes of technology that are designed to step up to the plate when GPS falls short. Navatar and Casio’s EX-H20G camera rely on a compass, accelerometers and pre-loaded maps, Smartsense and IndoorAtlas track a user’s movement through the Earth’s magnetic field, while UnLoc detects “invisible landmarks” to locate users.
DARPA researchers working at the University of Michigan have taken an approach somewhat similar to the Navatar and Casio systems with the creation of a “timing & inertial measurement unit” (TIMU).
The TIMU prototype contains a highly-accurate master clock and a six-axis inertial measurement unit consisting of three gyroscopes and three accelerometers. These give the device the ability to gather precise orientation, acceleration and time information to track a user’s position from A to B when contact with GPS satellites is temporarily lost.
The sensors are packed onto a single chip in six microfabricated layers that are each just 50 microns thick, which is approximately the thickness of a human hair. At just 10 cubic millimeters in size, the whole package is smaller than a U.S. penny.
“Both the structural layer of the sensors and the integrated package are made of silica,” said Andrei Shkel, DARPA program manager. “The hardness and the high-performance material properties of silica make it the material of choice for integrating all of these devices into a miniature package. The resulting TIMU is small enough and should be robust enough for applications (when GPS is unavailable or limited for a short period of time) such as personnel tracking, handheld navigation, small diameter munitions and small airborne platforms.”