On the Availability of GNSS and Terrestrial Location Techniques: A Field Study

Hybridization is a hot topic in the location field. Since there is no universal location technique that is capable of positioning in indoor and outdoor environments, two or more techniques must be coupled to produce a complete location solution. Accordingly, information on the availability of each of the techniques being coupled is of great relevance in the design and implementation stages of the location system. In public cellular networks, this coupling usually involves a terrestrial triangulation technique (e.g. E-OTD, OTDOA) and a GNSS-based technique (e.g. A-GPS). The purpose of this paper is twofold. Firstly, it presents a software tool developed for studying the availability of location systems in certain environments, which is able to capture and present information on the availability of satellites in the NAVSTAR constellation (i.e. GPS) and the GSM/GPRS base stations being received in the user terminal. Secondly, it studies the coverage of these techniques using the tool described. Availability data for three routes in an urban environment are gathered and analyzed. In two of them, GPS did not cover 100% of the route, which demonstrated the need to couple the technique with another terrestrial technique to cope with the "dark" areas.