Date of Award

Spring 1-1-2019

Document Type


Degree Name

Master of Science (MS)


Aerospace Engineering Sciences

First Advisor

Dennis M. Akos

Second Advisor

Nagaraj C. Shivaramaiah

Third Advisor

Jade Morton


In this thesis, a brief overview of the GPS L1 signal structure and GPS position and time estimation is given. Then, van Diggelen's A-GPS method is discussed with his millisecond ambiguity approach. Next, a way to accurately use any ambiguity time to reach nanosecond-level accuracy is developed. Experiments are then run to quantify the sensitivity of A-GPS to a priori errors in position and time, as well as the performance of the first sample time error as a function of ambiguity time. It is found that the safe zone for A-GPS is less than 35 km initial position error and less than 30 seconds initial time error. It is also found that an ambiguity time of 200 ms converges to nanosecond-level accuracy 99% of the time. Most first sample time errors are within one nanosecond while none exceed two nanoseconds as compared to a traditional GPS L1 SDR.