Integrated use of GPS and GLONASS in support of the redesign of road networks

An integrated GPS/GLONASS system was employed in this study to support the re-design of road networks and the adjustment of traffic control. The syste m was used to update road maps, and to determine the velocity and accelerat ion of a test vehicle. The vehicle ran along the traffic stream at designat ed times of a day, for specific time spans, to identify traffic conditions in urban areas of uncontrolled intersections such as roundabouts. Issues ad dressed included: transformation of GLONASS satellite coordinates from PZ-9 0 to WGS-84, the presence of the receiver clock error in the GLONASS double -differenced measurements, and the impact of the carrier wavelength variati on on the ambiguity resolution. Two tests were carried out in an urban envi ronment using the combined GPS/GLONASS system. The first test included upda ting a road map of a test area by an RTK approach. Results were checked by comparing them with an accurate map of the area, previously determined by c onventional methods. The second test comprised determining position, veloci ty and acceleration of a moving vehicle representing the traffic flow for a selected area. Different solution schemes were investigated, including: RT K, DGPS, and post-processing of phase measurements. The impact of GLONASS a ugmentation and the quality of GPS satellites on solution feasibility and a ccuracy were also examined. Test results showed the benefits of adopting th e integrated approach. These included: improving productivity and economics of map production, and improving availability, integrity, and accuracy of determining the velocity and acceleration, linked to positions on the road networks.