FIG Working Week 2000, 21-26 May, Prague

Integrated Systems and their Impact on the Future of Positioning, Navigation, and Mapping Applications

by Naser El-Sheimy

Key words: GPS, Inertial Systems, Navigational Aid, Vision-Based Systems. 


The Global Positioning System (GPS) is a constellation of satellites that broadcast signals that can be used to derive precise timing, location, and velocity information. The derived information (time, position, and velocity) may be combined with other systems such as communications devices, computers, and software to perform a variety of tasks.

The Global Positioning System (GPS) is capable of providing all range positioning accuracy in all situations where uninterrupted signal reception is possible and the general satellite geometry is within acceptable limits. It is also evident that other navigation technologies, such as Inertial Navigation Systems (INS), are currently not capable of providing similar accuracies at a comparable price, i.e. there is no real competition to GPS in a scenario of uninterrupted signal reception. This leaves two scenarios to be considered. The first one is that of intermittent signal reception, as for instance in heavily forested areas or in urban centres. The other one is that of no signal reception at all, as for instance in buildings, underground or underwater. In the first case, GPS has to be integrated with other sensors to bridge periods of no signal reception. In the second case, GPS has to be replaced by another system that can provide continuous navigation in those environments where GPS does not work. Both cases will be treated in this paper where the integration of systems and navigational aids (navaids), will be investigated as an alternative for times of no GPS signal reception. In terms of systems, both INS and vision-based systems will be considered. In terms of navaids, odometers, gyros and digital maps will be considered for land vehicle navigation, and pedometers, magnetic compasses, digital maps, and cellular phones for backpack systems.

Integrated systems will, therefore, provide a system that has superior performance in comparison with either a GPS, an INS, or vision-based stand-alone system. For instance, GPS derived positions have approximately white noise characteristics over the whole frequency range. The GPS-derived positions and velocities are therefore excellent external measurements for updating the INS and providing the imaging sensors with position parameters, thus improving its long-term accuracy. Similarly, the INS can provide precise position and velocity data for GPS signal acquisition and reacquisition after outages and the orientation parameters for the vision-based system. The vision-based system can be used as a backup navigation system and to update the INS data if the GPS signal is blocked for long periods. In general, the fact that redundant measurements are available for the determination of the vehicle trajectory parameters greatly enhances the reliability of the system.

The paper will cover both, the concept of integration and implementation aspects of integrated systems. Features common to most systems will be identified and factors affecting system performance will be discussed. All major features will be illustrated by examples. Finally, examples on future systems for mapping, positioning, and navigation applications will be given.

Dr. Naser El-Sheimy
Assistant Professor
Chair FIG C5 WG 1
Department of Geomatics Engineering
The University of Calgary
2500 University Dr.
N.W. Calgary

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