A MOBILE MULTI-SENSOR SYSTEM FOR GIS APPLICATIONS IN URBAN CENTERS 
Naser El-Sheimy 
Senior Engineer, GEOFIT Inc. 
Laval, Quebec, Canada 
Tel : (514) 978 9393, Fax : (514) 978 1963 
e-mail : nelsheim@geofit.ca 
ISPRS Commission II, Working Group 1 
Vienna, July 9-19, 1996 
KEY WORDS: Mobile Mapping System, The Global Positioning System (GPS), Inertial Navigation System (INS), CCD 
Cameras, Sensor Integration, System Calibration, Georeferencing of Video Images. 
ABSTRACT : 
A mobile highway mapping system has been jointly developed by The University of Calgary and GEOFIT Inc., a high-tech company in 
Laval, Quebec. The system named VISAT, stands for Video-Inertial-SATellite and integrates inertial and GPS technology with a 
cluster of CCD cameras. The overall objective was the development of precise multi-sensor mobile survey system that could be 
operated at a speed of 60 km per hour and achieve an accuracy of 0.3 m (RMS) with respect to given control and a relative accuracy of 
0.1 m (RMS) for points within a 35 m radius from the van. This accuracy is required in rural as well as in urban areas, including city 
centers. The updated GPS/INS information is used to georeference the images collected by the CCD cameras which record all details 
along the highway within a corridor of about 35 m. The shutters of the cameras and the output of the INS system are synchronized by 
the clock of the GPS receiver. 
A number of projects recently finished in Montreal and Quebec city provided the opportunity to test the system under different field 
conditions. Results of these tests are reported in this paper. A brief overview of system integration will be given followed by a detailed 
discussion of the system calibration. The analysis of recent field test will concentrate on the calibration results and the relative and 
absolute accuracy of the system. Overall, the results indicate that the required accuracies have been reached or surpassed by the current 
system. 
1. INTRODUCTION absolute accuracy of better than 0.3m if the distance to the van is 
35m or less. A workstation (GEOSTATION) facilitates the 
The dynamics of urban and rural development, the changes of quick selection and efficient storage of such features in a GIS 
land use and the increasing demand for precise Geographic system. 
Information Systems (GIS) in planning, make GIS information 
updating a permanent task. Keeping maps or GIS systems up to The system integrate a strap-down INS system, two L1/L2 GPS 
date is only possible to a limited extent. Even if the concept of receiver, eight CCD cameras, Anti-Braking-System (ABS), 
the classical map is changed to that of a digital map as a image control unit, and SVHS cameras. In the vehicle, all the 
consequence of technology available today, the core of the sensors are interfaced to a Pentium PC, which control different 
problem remains: ideally, data collection and storage has to be data streams through programmed hardware interrupt process 
continuous and the identification of changes must be reliable. software. For more details on the design of the VISAT system 
Classical methods of acquiring GIS data are no longer adequate see Schwarz e. al (1993a) and El-Sheimy et al (1995); for the 
because they are too slow and personnel-intensive. Satellite workstation design, see Li et al (1994). 
remote sensing and aerial photogrammetry can provide a variety 
of GIS information at very high data rates and at reasonable cost. 
However, the accuracy of satellite imagery is not sufficient for 
many GIS applications and the near vertical field of view of 
photogrammetric images provides only part of the information 
needed in urban centers. 
To address this problem, a mobile data acquisition system has 
been developed which generates georeferenced video images at a 
rapid rate. The system which was jointly developed by The 
University of Calgary and Geofit Inc., Laval, Quebec, is a Multi- 
sensor system, called VISAT, which integrates a cluster of 
digital cameras with an Inertial Navigation System (INS) and a 
pair of GPS receivers (Figure 1). It automatically collects 
georeferenced digital images along both sides of the road while 
moving at velocities of 50-60 km/h. Features of interest in these ; 
images can be selected in the office and positioned with an Figure 1 : The VISAT system. 
  
  
  
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996