New Scientist: Motion sensors could track troops when GPS cuts out
KNOWING where troops are during combat operations can be a matter of life and death – but GPS technology used to track troops is fragile, the signal easily lost. Now a UK company is developing a lightweight, wearable tracker that can provide location cover when GPS is down.
The system uses novel software to decipher position data from the signals generated by cheap microchip-based motion sensors – like those used in the Nintendo Wii and Apple iPhone.
The device is being developed by Tessella in Stevenage, Hertfordshire, which normally develops orientation software for spacecraft like the European Space Agency’s Herschel Space Observatory, launched last year. The software fuses data streaming from an on-board star-tracking camera with data from laser gyroscopes, enabling the system to gauge the craft’s position in space and its rotation.
These algorithms can also discern location when used with motion sensors, David Dungate of Tessella told the SpaceTech conference at the Rutherford Appleton lab in Oxfordshire, UK, last week. The motion sensor worn by the soldier is a matchbox-sized unit containing three microchip accelerometers and three gyroscopes mounted at right angles to each other. Using the data transmitted from this, the algorithm can work out the wearer’s position relative to a known start point – perhaps the point where GPS was lost.
The system would be less cumbersome than existing motion-sensing devices – footstep-detecting trackers worn on the foot or ankle, Dungate says. But the microchip sensors are prone to producing additional noise, resulting from variations in power supply, temperature and the like, making it tricky to get reliable data to work from.
Tessella is examining the noise produced by commercial motion sensors – like those used in smartphones – to look for characteristic patterns that filtering algorithms could use to determine which signals are relevant. These algorithms, or “Kalman filters”, use past data to predict how noise is likely to
affect a signal, aiming to produce measurements close to their true value. “We’re already showing that [applying the algorithm to] some of the data correctly eliminates errors,” says Dungate. “Our algorithms wring the data’s neck to get every last bit of info.”
The company hopes to have its tracker working in six months, and claims defence contractors have already shown interest.
If it works, it will be boon way beyond the military, says Bob Cockshott, head of location and timing at the UK’s National Physical Laboratory in Teddington, Middlesex. “There’s a huge need for a non-GPS technology, not only for use when jamming is being used, but locations like urban canyons where GPS simply can’t reach.”
Source: New Scientist
