Time-Diverse Doppler-only LEO PNT: Initial Solution

This paper develops Doppler-based Geometric Dilution of Precision (D-GDOP) analysis for time-diverse Doppler-only positioning and presents an associated batch filter. The former Doppler-only positioning solution requires at least eight satellites to be view simultaneously and discards previous Doppler measurements. In cases where fewer than eight satellites are available, using Doppler measurements from multiple points in time allows a complete solution to be determined. In cases where eight or more are available, using additional time-samples can further reduce D-GDOP and improve positioning accuracy. This work presents an initial batch filter solution that assumes constant velocity and constant clock-offset rate. By considering an additional 10 seconds of previous measurements, position and clock-offset errors were cut in half. However, because these assumptions are unrealistic for significant time spans this work also presents and tests an initial time-varying Kalman filter model and defines a D-GDOP metric for it.