Navigating Urban Areas by VISAT—A Mobile Mapping System Integrating GPS/INS/Digital Cameras for GIS Applications

Following a brief system description of VISAT (Video, Inertial, and SATellite GPS), a mobile survey system for the establishment of geographic information systems (GIS) in urban centers, the quality control component of the system and results of a performance analysis are discussed. Data collected in test networks in Calgary, Denver, and Laval City are used to assess system performance in terms of accuracy and reliability, and to develop a real-time quality control algorithm for the navigation sensors. Special attention is given to detecting and fixing GPS cycle slips by applying independent inertial navigation system (INS) trajectory data. In urban centers where, because of tree coverage and shading by buildings, frequent cycle slips are the rule rather than the exception, the effectiveness of INS bridging is crucial for overall performance. Results show that system specifications have been met, and in many cases performance is better than specified.