Augmentation of a navigation reference system with differential global positioning system pseudorange measurements

To quantify the performance of navigation systems, the US Air Force has used a baseline navigation system, the Completely Integrated Reference Instrumentation System (CIRIS), which obtains an accurate navigation solution by combining information from three major subsystems. Although the navigation solution produced by CIRIS is accurate, it will soon be inadequate as the standard against which future navigation systems can be tested. The authors propose an alternative to CIRIS, a hybrid Enhanced Navigation Reference System (ENRS) which takes advantage of a newer ring laser gyro strapdown inertial navigation system (INS), certain features of the current CIRIS, and certain features of differential Global Positioning System (DGPS) measurements. Analysis conducted using a Kalman filter development package known as the Multimode Simulation for Optimal Filter Evaluation (MSOFE) is presented. Both a large order baseline truth model for the ENRS and full- and reduced-order Kalman filters are developed