This diploma thesis examines procedures of position reckoning, which have been implemented on a vehicle on-board computer made by INIT. First the original method for dead reckoning using the odometer signal is described. Several sensor-based methods were examined.
At the moment there is no alternative for the GPS-system. The civilian version of the Russian GLONASS is much less precise and the European Galileo-System will not be operational before 2008. Absolute position reckoning by locating cellular phones is not an option because it is less precise than GPS, even in areas with good radio coverage.
The Swiss company u-Blox offers a combined solution for dead reckoning based on GPS, a gyrosensor and an odometer signal. Without GPS-reception the current location is calculated from the values of the odometer signal and the gyrosensor.
Measured positions are transmitted to the on-board computer as NMEA-telegrams. To further increase the accuracy of the location tracking, the values are supported by map data. According to experiments a suitable partitioning of the roadmap data in tiles was implemented to allow a fast search in the data while keeping a low memory profile.
Several improvement methods have been tested. A graphical representation of the data allows a simple evaluation of these methods. According to the test results the best improvement method for each situation is selected.
By using the map support, the position reckoning is improved even without additional sensors. Map support together with a sensor enhanced GPS-receiver results in a significant increase in accuracy of the position reckoning.