Date of Award

3-13-2009

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering

Department

Department of Electrical and Computer Engineering

First Advisor

John F. Raquet, PhD

Abstract

The 746th TS uses a flight reference system referred to as the Central Inertial and GPS Test Facility (CIGTF) Reference System (CRS). Currently the CRS is the modern standard flight reference system for navigation testing, but high accuracy is dependent on the availability of GPS. A pseudolite system is currently being developed to augment the CRS and supply the capability to maintain high accuracy navigation under normal and jamming conditions. Pseudolite measurements typically contain cycle slips and other errors (such as multipath, tropospheric error, measurement noise) that can affect reliability. Past work relied on the receiver-reported signal-to-noise (SNR) value to determine whether or not a cycle slip occurred. However it has been shown that even when the SNR is relatively high, a cycle clip can occur. To reduce the error in the pseudolite measurements, the pseudolite system was integrated with an inertial navigation sys- tem (INS). The integrated system detects failures through residual monitoring using a likelihood function. Integrating the inertial sensor provides a means for a filter to maintain the reliability of the pseudolite data which, in turn, increases the integrity of the resulting navigation solution. An experiment was conducted using six pseudolites and a ground vehicle equipped with a pseudolite receiver, and both a commercial-grade and tactical-grade inertial systems. The inertial data was combined with both real and simulated data to evaluate cycle slip detection performance. Results from this experiment have shown cycle slips in the carrier phase measurements were detected and corrected using both commercial-grade and tactical- grade INS, but that performance, in terms of probability of detection and time to detect, was improved with the higher quality inertial data.

AFIT Designator

AFIT-GE-ENG-09-08

DTIC Accession Number

ADA499623

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