Combining pseudoranges from GPS and Loran-C for air navigation

Position fixing, receiver autonomous fault detection, and receiver autonomous fault isolation are treated as system services, and the probability of outage for these three services is computed. The outage probability for the level of service required for nonprecision approach and enroute navigation in the National Airspace System is computed. The analysis assumes that GPS (Global Positioning System) is configured in the Optimal 21 constellation and includes the effects of satellite as well as Loran station failures. it is pointed out that user equipment which combines pseudoranges from GPS and Loran would be more reliable than an unaided GPS receiver or a Loran-only receiver. It could remove coverage outages caused by satellite failures and/or bad satellite geometry. Similarly, it could remove most of the coverage outages caused by Loran station shutdowns, high atmospheric noise levels, or precipitation static. A hybrid GPS/Loran receiver could also reliably provide self-contained fault detection and isolation (otherwise known as receiver autonomous integrity monitoring)