Navigation System Integrity Monitoring Using Redundant Measurements

Abstract

The advantages of a navigation system that can monitor its own integrity are obvious. Integrity monitoring requires that the navigation system detect faulty measurement sources before they corrupt the outputs. This paper describes a parity approach to measurement error detection when redundant measurements are available. The general form of the detector operating characteristic (DOC) is developed. This equation relates the probability of missed detection to the probability of false alarm, the measurement observation matrix, and the ratio of the detectable bias shift to the standard deviation of the measurement noise. Two applications are presented: skewed axis strapdown inertial navigation systems, where DOCs are used to compare the integrity monitoring capabilities of various redundant sensor strapdown system configurations; and GPS navigation sets, where DOCs are used to discuss GPS integrity monitoring for meeting non-precision approach requirements. A fault identification algorithm is also presented.