Global navigation satellite systems (GNSS) are an essential component in many areas of our daily life. They find application in diverse fields of private, commercial and scientific activities and are employed to meet the needs of police and military. Their fundamental importance for industrial countries is not the least the triggering point for the continuing modernisation of the existing and the development of new systems. The global satellite navigation systems are supplemented by regional satellite navigation systems (RNSS) and satellite based augmentation systems (SBAS). The diversity of systems, applied signal modulations and carrier frequencies, in particular in their combination, provide a broad range of opportunities along with new challenges.
The work presented herein focuses on the use of satellite navigation systems for precise positioning and timing applications and scientific analysis. For best and comprehensive results, an equivalent combination of all available systems and signals is a fundamental requirement. For these reasons, relative approaches based on observation differences are rather inappropriate. Hence, this thesis focuses primarily on the method of precise point positioning (PPP) by waiving linear combinations. The objective is the development of a universal PPP analysis approach for standalone PPP and network solutions. Raw observations conserve the physical properties of original observation. This allows a detailed analysis of individual signal characteristics, but leads to the necessity of handling them. The utilisation of raw observations comes along with maximum flexibility. It allows for the application of physical error models as well as individual weighting and edition of all individual observation types. The possibility of a joint processing of all observations and the estimation of all parameters in a single run results in a significant simplification of the processing procedure.
The first part of the thesis provides a general introduction to conventional GNSS analysis and highlights the limitations thereof. The second part introduces the technique of raw observations processing. It highlights the differences from the common ionosphere free processing approach and discusses the challenges. The concept presented for the analysis of GNSS raw observations is flexible and adjustable to any kind of GNSS application. This flexibility is attributed to a variety of different possible interpretations of the raw observation equation. In the frame of this thesis, a selection of different interpretations is introduced and demonstrated. One of the most important parameters for the analysis of raw observations is the so-called uncalibrated signal delays. The work presented exemplarily demonstrates their characteristics and discusses their implications for the analysis.
For maximum stability of the results, it is common practice to resolve and apply integer carrier phase ambiguities. The presented work discusses and demonstrates the feasibility of this methodology for the implemented approach. It shows that the new approach simplifies the resolution of inter-GNSS carrier phase ambiguities and extends the spectrum of resolvable ambiguities.
It is demonstrated that the proposed concept provides an “at least” equivalent alternative to the common processing strategies, applicable for highly precise standalone, as well as network PPP solutions, allowing for the simplified, consistent processing of different numbers of observation, suitable for an optimal, flexible, equivalent, joint processing of arbitrary GNSS observation types. It introduces a new dimension of analysis, with direct access to all individual observations and parameters
