Stochastic modeling of atomic receiver clock for high integrity GPS navigation

The Global Positioning System (GPS) was designed as a passive radio navigation system to provide positioning capability without the need for receiver clock synchronization to GPS time. In theory, a GPS receiver equipped with a high-quality receiver clock can provide better system performance. More importantly for integrity-driven navigation applications, the additional redundancy provided by a clock dynamic model can increase fault detection performance and availability for receiver autonomous integrity monitoring (RAIM). In the work presented here, a stochastic model is used to rigorously account for the time correlation of random errors in high-quality GPS receiver clocks. A batch estimator (BE) is then developed to use GPS measurements collected over time to estimate current user position. The BE incorporates the stochastic clock model to ensure that position errors are properly quantified and, therefore, that navigation integrity is ensured. The resulting improvement in positioning performance is demonstrated using covariance analysis.