GNSS Positioning in Non-line-of-Sight Context-a Survey

The reliable and accurate localization of people and vehicles is one of the challenges of intelligent transportation systems (ITS) s. This has led to a variety of technical approaches in recent years. Towards an exact positioning via Global Navigation Satellite Systems (GNSS) s the visibility of satellites is an important factor. In this paper, we review the literature regarding the positioning under non-line-of-sight conditions and analyze a range of topics from explicit modeling to empirical data collection. The variety of research indicates the growing interest in reliable and accurate localization in urban areas. Moreover, the development and application of different techniques also suggest the existence of many avenues for further exploration. Accordingly, we develop a taxonomy of the technical design for GNSS applications dealing with NLOS and a typology of the measuring instruments based on an extensive analysis of the state of the art. Thus, the goal of this work is to provide a starting point regarding the state of the art for further research activities in robust GNSS positioning.