Global Positioning System/Inertial Measurement Unit Ultra-Tightly Coupled Integrity Monitoring

"We propose to develop a Global Positioning Satellite/Inertial Measurement Unit(GPS/IMU) integrity monitor using techniques that can be implemented in parallel. The first technique takes advantage of the GPS link modulation, namely spreadspectrum coding and bi-phase shift keying. A multiple step procedure will allow spectrum monitoring for downlink integrity, increased background noise, jamming and interference. This procedure will detect changes in the general noise background, the presence of several types of jamming and interference signals. It will also estimate, track the frequency difference of arrivalbetween the downlinks and provide separate, independent geolocation andvelocity estimates. The second technique will examine the modeling assumptions of the system errors. Two filters will be developed each based on differentprobability density functions. A detection criteria will be derived that compares the two filter outputs to a given threshold to determine whether or not the receiver integrity has been compromised An IMU integrity monitor will be developed using trend analysis and frequency rate residuals analysis of therate data. Archived data taken during previous aircraft experiments will be used to verify and validate the model. The algorithms will be developed anddemonstrated using Avtec's heritage GPS receiver simulator. The anticipated benefits and commercialization strategy of the successfulcompletion of the