Metrology of urban moving by G.P.S

Concerns the quantification of the accuracy of systems of vehicle location in urban areas. The problem is more difficult than in the countryside. Towns are indeed very special places regarding the traffic: variable and rather slow speed, change of lane or route, various masking (narrow streets, trees, tunnels or bridges), and different cases of electromagnetic disturbances and reflections. Another purpose is to offer an alternative and automatic system to the travel time measurement existing at present in several towns and called MITEMPS (Computerized measurement of travel time), which requires manual switching by the operator, in front of pre-defined static beacons. In particular, the article discusses a dynamic positioning system for urban areas, based on GPS (Global Positioning System), better than 5m for 95% of measurements.