Aerial Vehicle Protection Level Reduction by Fusing GNSS and Terrestrial Signals of Opportunity

A method for reducing the protection levels (PLs) of aerial vehicles by fusing global navigation satellite systems (GNSS) signals with terrestrial signals of opportunity (SOPs) is developed. PL is a navigation integrity parameter that guarantees the probability of position error exceeding a certain value to be bounded by a target integrity risk. For unmanned aerial vehicles (UAVs), it is desirable to achieve as tight PLs as possible. This paper characterizes terrestrial cellular SOPs' measurement errors from extensive UAV flight campaigns, collected over the past few years in different environments and from different providers, transmitting at different frequencies and bandwidths. Next, the reduction in PLs due to fusing terrestrial SOPs with a traditional GNSS-based navigation system is analyzed. It is demonstrated that incorporating terrestrial SOP measurements is more effective in reducing the PLs over adding GNSS measurements. Experimental results are presented for a UAV traversing a trajectory of 823 m, during which the VPL of the GPS-based and GNSS-based navigation systems were reduced by 56.9% and 58.8%, respectively, upon incorporating SOPs; while the HPL of the GPS-based and GNSS-based navigation systems were reduced by 82.4% and 74.6%, respectively, upon incorporating SOPs.