Performance Evaluation of EGNOS in Challenging Environments

Space-based augmentation systems (SBAS), such as EGNOS, are largely used to complement GPS for accurate and reliable positioning, which is required by rapidly growing location-based services (LBS). However, it is challenging to use EGNOS in the environments including urban areas and marginal area of the monitoring networks, where many LBS are delivered. Through the experiments in the challenging observation conditions, this study first evaluates the performance of EGNOS in these environments. Challenges consist in two aspects: EGNOS signals may be interrupted by blockages; EGNOS messages are not produced at all for marginal geographical areas due to the lack of raw satellite measurements. In order to use EGNOS for enhanced positioning performance in these environments, this paper then discusses several potential solutions. It is concluded that the two autonomous approaches, i.e. using aged corrections and mixing corrected and uncorrected satellites, can improve the positioning accuracy with a stand-alone receiver, and a full EGNOS positioning performance can be achieved in urban areas via a terrestrial access to EGNOS data, for example, the Internet connection with a smartphone. This paper discusses the effectiveness and usability of these approaches.