System Calibration of Land-baed Mobile Mapping Systems

The increasing demand for up-to-date 3-D geographic information systems (GIS) data for planning, transportation, and utility management applications poses significant challenges to the Geomatics community. Of all the challenges in acquiring, building, maintaining, and using GIS, none is more central than that of data acquisition. Obtaining the required spatial and attribute data by conventional methods such as aerial photogrammetry and terrestrial surveying is expensive and time consuming. These methods are, therefore, not well suited for rapid updating of GIS databases. Fortunately, the development of land-based mobile mapping systems (MMS) has opened a new avenue to meet these challenges. Land-based MMS are capable of providing fast, efficient, cost-effective and complete data acquisition systems. As such, they are an innovative technology for creating and updating 3-D GIS databases both quickly and inexpensively. The delivered accuracy of MMS is a function of several parameters. This includes the accuracy of the navigation component which provides the absolute location and orientation of the system. Individual sensor calibration provides models for correcting their measurements systematic errors. Total system calibration is a key factor in MMS performance. In this step, the geometric relationship between the mapping sensor and the navigation sensor is estimated. This involves the determination of the camera perspective centre location with respect to the Inertial Navigation Systems (INS) triad centre which is typically part of the navigation component. Also, the rotation angles between the camera axes and the INS axes are estimated. In this paper, we report our experience in calibrating the VISAT TM (Video-Inertia-SATellite) mobile mapping system which is developed by Absolute Mapping Solution Inc. The paper presents the different alternatives in boresight calibration. A project recently finished in Calgary, Canada, provided the opportunity to test the system under different field conditions. Results of these tests are reported in this paper with more emphasis on the impact of system calibration on the absolute and relative accuracy of the VISAT system.