The development of VISAT: A mobile survey system for GIS applications.

摘要

During the last decade, the demand for Geographic Information Systems (GIS) in management and design applications has greatly increased. The realization of a GIS in many application areas still suffers from data acquisition problems. To be of value to the user, a GIS must be updated regularly, so that the information in the database correctly represents the real world. However, the acquisition of up-to-date GIS data by conventional survey techniques is prohibitive in cost and has therefore limited the applicability and usefulness of GIS to potential users. Described in this thesis is an attempt to overcome this problem by employing a mobile highway survey system and an associated workstation for georeferenced images.; The total system consists of a data acquisition system, called VISAT, and a data processing system, called VISAT Station. In this thesis, only the first component will be addressed. The data acquisition system has been designed and implemented in cooperation between The University of Calgary (UofC) and GEOFIT Inc. The system can be used to create and selectively update GIS databases very quickly and inexpensively. The system derives its name, VISAT, from the fact that it utilizes Video images, an INS system, and the GPS Satellite system. The system integrates a cluster of Charge-Coupled-Devices (CCD) cameras, an Inertial Navigation System (INS), and satellite receivers of the Global Positioning System (GPS). The system carrier is currently a van, but the use of the system in airborne or marine mode can be realized in a similar way. For the van application, the overall objective was the development of a precise mobile highway survey system that could be operated at a speed of 60 km per hour and could achieve an accuracy of 0.3 m (RMS) with respect to the given control framework and a relative accuracy of 0.1 m (RMS) for points within a 35 m radius. This accuracy was required in all environments including inner cities, where a stand-alone GPS is not reliable. Sensor integration has been optimized to reliably reach the accuracy requirements in different environments. Data flow optimization has been done with the objective of facilitating the subsequent feature extraction process and transfer into a GIS system.; System testing indicates that highway velocities of 60 km/h can be maintained with adequate data transfer and target positioning in a post-processing mode with the VISAT Station software. Extensive tests in city centers, suburban areas, and rural areas have shown that the run-to-run and day-to-day repeatability achieved is about 10 cm (RMS) in horizontal and about 5 cm (RMS) in height and that the expected absolute positioning accuracy of 30 cm is surpassed in many cases.