Improving Navigation in GNSS-challenging Environments: Multi-UAS Cooperation and Generalized Dilution of Precision

This paper presents an approach to tackle navigation challenges for Unmanned Aircraft Systems flying under non nominal GNSS coverage. The concept used to improve navigation performance in these environments consists in using one or more cooperative platforms and relative sensing measurements (based on vision and/or ranging) to the navigation aid. The paper details the cooperative navigation filter which can exploit multiple cooperative platforms and multiple relative measurements, while also using partial GNSS information. The achievable navigation accuracy can be predicted using the concept of "generalized dilution of precision", which derives from applying the idea of dilution of precision to the mathematical structure of the cooperative navigation filter. Values and trends of generalized dilution of precision are discussed as a function of the relative geometry in common GNSS-challenging scenarios. Finally, navigation performance is assessed based on simulations and on multi-drone flight tests.