Date of Award

3-10-2010

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Michael Stepaniak, PhD

Abstract

In modern warfare navigation services are very important. GPS is currently providing service for accurate navigation, except in some areas, especially urban areas, where GPS signals cannot always be tracked by users. In these cases some additional navigation support could be provided by other global navigation satellite systems. If GPS is combined with other navigation systems than the navigation gap will be minor. In this thesis, the effect of combining GPS with other satellite navigation systems, specifically GLONASS, Galileo and Compass, is evaluated in terms of availability and position dilution of precision (PDOP) values. First, satellite constellations are simulated in Satellite Tool Kit (STK) to generate ephemeris data. A street scenario is then established for simulating different elevation mask angles to represent urban and mountainous areas. The performance of the combined system is also evaluated as a function of the uncertainty in the time offset between systems. Combined GPS/GLONASS and GPS/Compass solutions showed little improvement for low elevation mask angles, however they provided some enhancement for higher elevation angles. Combined GPS/Galileo performance was improved for all elevation angles compared to only GPS, GPS/GLONASS, and GPS/Compass. The best results for availability and PDOP were obtained from combining all four systems. Although using satellites from other constellations enhances availability and decreases errors. It also brings dependency on other systems other than GPS. Adding two satellites from only the Galileo constellation to GPS is shown to be a configuration with a good compromise between dependency and performance.

AFIT Designator

AFIT-GSS-ENG-10-01

DTIC Accession Number

ADA517266

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