Applications in related fields

This field of research involves the determination of the parameters which were not anticipated when GNSS were designed. For example, GNSS measurements include important information concerning the atmospheric condition along the signal-path or multi-path signals might provide information about the geometrical and electro-magnetical environment. As for the latter, this has led to a new research field called GNSS reflectometry (GNSS-R). Since GNSS signals, which are reflected by water, ice or land surfaces, interact differently with the direct signals of the satellites one can deduce information about the reflecting surfaces. Geophysical features (e.g. geometric height, soil moisture, snow height, …) of the reflecting surfaces can be retrieved and be provided for weather forecasts or climate research. In a similar way, the determination of atmospheric parameters using GNSS has been another success story. Especially the determination of integrated water vapor from GNSS contributes to the improvement of the global and regional weather forecasts and has impact on different scientific projects.

In addition to these applications, research on time- and frequency generation and dissemination is being carried out. Time as the third component of positioning, navigation and timing (PNT) is a crucial component for many applications in science, industry and society. Considering that the next-generation of atomic clocks are several orders of magnitude more stable than current frequency standards, it is evident that the requirements on GNSS-based time and frequency transfer are going to increase. The INS has set put a special research focus on this topic as well.

Reliable monitoring of water vapor content and dynamics in the troposphere represents one of the most demanding challenges in modern atmospheric remote sensing. Due to the high spatio-temporal variability of this parameter, traditional measurement systems often fail to offer the required resolution. Since water vapor directly affects the path and propagation speed of microwave navigation signals, this phenomenon must be precisely accounted for in high-accuracy GNSS applications, including geodesy and geophysics. Based on observations from ground-based GNSS networks, it is possible to reconstruct the three-dimensional distribution of atmospheric water vapor using GNSS tomography. However, this technique relies on a two-step computational process that utilizes intermediate products and simplified mapping of GNSS signal delay, which limits the final reliability of the results.

Read more about the DFG Project “Simultaneous Troposphere Estimation with Precise Point Positioning (STEPPP)” in the Project Summary.