VISAT - A Mobile System for Precise GIS Highway Inventory Applications

摘要

VISAT is a system jointly developed by a research team at the University of Calgary and Geofit Inc. of Laval, Quebec. It stands for Video-Inertial-SATellite and integrates inertial and GPS satellite technology with a cluster of CCD cameras (Charge-Coupled Devices) in order to map a highway corridor of about 50m to each side of the highway. Mapping is typically done at a speed of 50 to 60km/h, positioning all features in the corridor with an accuracy of 30cm or better with respect to the GPS reference. Accuracies with respect to the camera reference are of the order of 10cm. An analysis of test results obtained from the prototype system demonstrates that the design accuracies have been achieved. In this paper, a brief description of the sensors and the essential features of the system design are given, followed by a discussion of the data management process which transforms digital image coordinates into three-dimensional coordinates. These are then transformed into points, arcs, or polygons to be used as elements in a GIS highway inventory system. The system offers a number of unique features which make it a versatile tool for highway survey and GIS applications. The field system can be operated without GPS input which makes it suitable for operation in inner cities and heavily treed areas. Field measurements are automated and completely separated from the measurement of specific image features which are done on a workstation. Images from different runs can be used on the workstation because each image is individually georeferenced. Measured GIS elements can be directly displayed with an existing base map and, thus, map updating becomes easy. A discussion of some of the features to be included in the future system development concludes the paper.