VISAT: A Mobile City Survey System of High Accuracy

Naser El-Sheimy, Klaus-Peter Schwarz, Ming Wei, Martin Lavigne

Abstract:	This paper assesses the performance of VISAT, a mobile city survey system, for Geographic Information System (GIS) applications in urban centers. In this system, jointly developed by the University of Calgary and Geofit Inc., GPS and INS provide the position and attitude, while a cluster of video cameras produce a set of 8 images at each exposure. The three sensors are mounted on a road vehicle moving with a velocity of 50-60 Km/h. The overall objective of the system is to reach object coordinates with an accuracy of 30 cm for objects within 30m from the van. The GPS position and velocity will control the INS error propagation, and the high frequency INS position output bridges GPS outages, corrects cycle slips, and gives precise interpolation between GPS updates. The updated GPS/lNS information is used to georeference the video images. The system is synchronized by the clock Pulse Per Second (PPS) of the GPS receiver and the logging PC real-time-clock chip. In this paper a brief description of the production system sensor integration and the essential features of the system design is given. Data collected in test networks in Calgary and Lava1 City will be used to assess the system performance in terms of accuracy and reliability. The concept of using INS positions to detect and fix GPS cycle slips will be investigated using data collected in the Laval city test network where frequent cycle slips occur due to tree coverage. Special emphasis is given to GPS performance in urban areas and the effectiveness of INS bridging in this case.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	1307 - 1315
Cite this article:	El-Sheimy, Naser, Schwarz, Klaus-Peter, Wei, Ming, Lavigne, Martin, "VISAT: A Mobile City Survey System of High Accuracy," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 1307-1315.
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