Evaluation of satellite based traffic data using compartments flow model and particles filtering

Kurzfassung

With the recent revolution in telecommunication technologies, individual mobility is facing a trend towards massively enhanced travel experience with huge amounts of localised information. In the sector of road transportation, real-time traffic information eases individual users travel choices and navigations while contributing to global improved safety and efficiency. This soaring needs for information goes along with the crucial necessity of developing new sources of highly reliable traffic data and new modes of provisions. In this document, we present the results of a study carried out at the German Aerospace Center (DLR) on a new radar based ground moving objects detection technology implemented in the satellite TerraSAR-X. Its device is able to detect and measure vehicles speeds over very large areas almost instantaneously. This study was aimed at developing a standalone module enabling to compare traffic data from the satellite system to ground based measurements. The requirements of DLR regarding the comparison module were formalised under three types of analysis that it must enable: - comparison of travel times; - comparison of speed profiles; - evaluation of the detection rate. As both sources provide traffic information from two inconsistent prospectives, the basic idea for comparison was to extrapolate discrete spatial data from ground sensors at the time of satellite acquisition tsat. To do so, a macroscopic traffic model was implemented which allows to simulate the evolution of conditions over time using a particles filtering technique. An estimated distribution of vehicles positions and speeds at tsat can thus be determined from which desired quantities such as travel time, local speed and detection rate can be derived. The results of numerical applications on six test data sets proved the methodology to be functional and entirely reproductible. Though restricted in magnitude because of the limited number of acquisitions processed, the outputs tend to show that travel time and speed informations derived from TerraSAR-X data provide a trustworthy insight of instantaneous traffic conditions. Results regarding detection rate estimations are consistent with theoretical expectations and thus support the validity of both the detection system and the evaluation method.