Mobile Indicators in GIS and GPS Positioning Accuracy in Cities Artur Janowski 1 , Aleksander Nowak 2 , Marek Przyborski 2 , Jakub Szulwic 2 1 University of Warmia and Mazury, Faculty of Geodesy and Land Management, Institute of Geodesy, Olsztyn, Poland artur.janowski@geodezja.pl 2 Gdansk University of Technology, Faculty of Civil and Environmental Engineering, Department of Geodesy, Gdansk, Poland {aleksander.nowak,marek.przyborski,jakub.szulwic}@pg.gda.pl Abstract. The publication describes the possible use of tele-geoprocessing as a synergy of modern IT solutions, telecommunications and GIS algorithms. The paper presents a possibility of urban traffic monitoring with the use of mobile GIS indicators of dedicated monitoring system designed for taxi corporation. The system is based on a stationary and mobile software package. The optimal and minimal assumptions for the monitoring of urban traffic are described. They can be implemented as a verification or supplementary tool for complex and high cost transportation management systems or throughput of city streets monitoring systems. The authors show limitations of standard monitoring and GNSS positioning in urban area. They indicate the possible improvement in the functionality of the application to the calculation of supplementary vector data of possible trajectories and based on it, the correction of the data received from the satellite positioning. Keywords: mobile GIS indicators, urban traffic monitoring, limitation of GNSS in traffic monitoring 1 Introduction Contemporary technological availability of GNSS positioning (Global Navigation Satellite System), in particular GPS-NAVSTAR (Global Positioning System - NAVigation Signal Timing And Ranging), the ability to use a wide range of solutions and algorithms in the field of information systems (GIS, Geographic Information System) and still permanently increasing and required fulfilling expectations of the information society implies a significant development of all services dedicated to the general urban population. The consequence of this is also the noticeable and continuous development of the IT service of taxi corporations. Increasingly important is also the reliability and availability of GNSS positioning in compact urban development. The problem is connected with the constantly moving GNSS receiver and the variability of this movement (which is the consequence of this movement) and impact of field screens. It requires the use of appropriate corrective algorithms,