This contribution proposes a positioning system that fuses GPS pseudoranges and WLAN ranges when fewer than four GPS satellites are available. In order to enhance as much as possible the positioning availability, a tight hybridization approach with both technologies is considered. Although the work has been performed considering WLAN and GPS, most of the presented ideas, procedures and results are also valid for generic tight non-synchronised fusion of GNSS with terrestrial signals. Special emphasis is dedicated to the phenomenon of positioning ambiguity that appears due to the incorporation of the terrestrial measurements. In order to solve this ambiguity, a method is proposed and explained. Later, the method and the availability and the accuracy of the system are tested considering different satellite and terrestrial geometries. Results show that the proposed system is able to improve the availability while maintaining the accuracy of GPS alone.

Peer Reviewed