A low cost navigation unit for positioning of personnel after loss of GPS position

We have built a test unit containing a GPS, an inertial measurement unit, magnetometers and a barometer. When the GPS looses its signals, the other sensors are used to keep track of the position. Unscented Kalman filters have been used to test the performance of different aid sensor configurations. In addition to the four different sensor configurations, the gyroscope output was filtered, making it eight different test scenarios. Simulations show that filtering the gyroscope output and using inertial sensors in addition to a barometer had the lowest position error, with a standard deviation of the position of 8.5 m. For unfiltered gyroscope output the best result was obtained when using all sensors. This had a standard deviation of the position of approximatly 42 m. The preliminary real world test results had a much larger error than the simulation.