Marcus Franz GLANER
Towards instantaneous PPP convergence using multiple GNSS signals
Dienstag, dem 04. Oktober 2022, 15:00
Seminarraum DA02A (grüner Bereich, 2. Stock), Wiedner Hauptstraße 8, 1040 Wien
Over the past decades, the principle of Precise Point Positioning (PPP) has become a wellestablished technique for determining the user's position with Global Navigation Satellite Systems' (GNSS) signals. A position accuracy at the centimeter or even millimeter level is accomplished by using code and phase observations, exploiting precise satellite products (e.g. orbits, clocks, and biases), and applying sophisticated algorithms. However, the convergence time until the coordinates have reached this accuracy is well known as the primary concern of PPP. Typically, the convergence time of a PPP solution using GPS observations is 20-30 minutes, even with favorable satellite geometry.
The main objective of this thesis is to develop PPP processing schemes reducing the coordinate convergence time as far as possible. Therefore, multi-frequency signals of all four globally-working GNSS are exploited and used to estimate the user's position. The uncombined model is developed as an alternative to the observation model of the conventional PPP approach using the ionosphere-free linear combination. This flexible model is based on the raw GNSS observation equations and shows several benefits compared with the ionosphere-free linear combination. For example, the raw observation noise is preserved and ionospheric pseudo-observations are included in the calculation of the PPP solution, resulting in the uncombined model with ionospheric constraint. Finally, integer ambiguity resolution is performed in the conventional as well as the uncombined model. The presented approaches, models, and algorithms are implemented in raPPPid, the PPP module of the Vienna VLBI and Satellite Software (VieVS). This software was developed in the course of this thesis. With raPPPid, convergence times of 1 minute or below to centimeter-level position accuracy are achieved for static receivers under good conditions.