Date of Award


Document Type


Degree Name

Master of Science


Department of Electrical and Computer Engineering

First Advisor

Richard K. Martin, PhD.


The Global Positioning System (GPS) provides world-wide availability to high-accuracy navigation and positioning information. However, the threats to GPS are increasing, and many limitations of GPS are being encountered. Simultaneously, systems previously considered as viable backups or supplements to GPS are being shut down. This creates the need for system alternatives. Navigation using signals of opportunity (SoOP) exploits any signal that is available in a given area, regardless of whether or not the original intent of the signal was for navigation. Common techniques to compute a position estimate using SoOP include received signal strength, angle of arrival, time of arrival, and time difference of arrival (TDOA). To estimate the position of a SoOP receiver, existing TDOA algorithms require one reference receiver and multiple transmitters, all with precisely known positions. This thesis considers modifications to an existing algorithm to produce a comparable position estimate without requiring precise a priori knowledge of the transmitters or reference receiver(s). Using Amplitude Modulation (AM) SoOP, the effect of erroneous a priori data on the existing algorithm are investigated. A proof-of-concept for three new estimation algorithms is presented in this research. Two of the estimators successfully demonstrate comparable performance to the existing algorithm. This is demonstrated in six different transmitter environments using four different receiver configurations.

AFIT Designator


DTIC Accession Number