ITRF4future - Innovative strategies for future ITRF solutions

• Applicant: Dr.-Ing. Manuela Seitz
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547865164

The realization of the International Terrestrial Reference System (ITRS) serves as the basis for nearly all geodetic applications, providing the reference for observations, monitoring derived geodetic parameters, and researching geophysical phenomena reflected by parameter time series. The recently published ITRS realizations, the ITRF2020, DTRF2020, and JTRF2020, show differences in estimated station coordinates and velocities of up to several millimeters and about 1 mm/yr, respectively. These differences can grow up to several centimeters when International Terrestrial Reference Frame (ITRF) solutions are extrapolated over a few years. Differences between the ITRF solutions mainly concern the combination strategies used, the treatment of non-linear station motions and the realization of the scale. The scale is directly related to the consistently estimated station heights and is therefore essential for all applications related to the height. A prominent example is the determination of global sea level rise. Basis for the generation of ITRF solutions are the solution series of the four space geodetic techniques: Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). Model developments were performed recently for both, SLR and VLBI observation analysis. First analyses indicate the high sensitivity of the realized scale. Independent from this development, GNSS became able to provide scale information due to the disclosure of the precise calibration of antennas of Galileo satellites by the European GNSS Agency. Our project investigates the sensitivity of the scale derived by SLR, VLBI and GNSS with respect to new technique-specific and general models and aims to draw conclusions from the comparison of ITRF2020, DTRF2020 and JTRF2020. Second, we will develop a strategy to compare scales derived from different techniques with high accuracy. The comparison also serves as cross-validation and allows conclusions to be drawn about the effects of model changes on scale agreement and the accuracy of scale realization in the ITRF today. In the third part, a strategy for the realization of the ITRS is developed based on the exploitation of the strengths of all four observation techniques involved. We will discuss the results regarding the ambitious International Association of Geodesy (IAG) Global Geodetic Observing System (GGOS) requirements of 1 mm accuracy and 1 mm/decade long-term stability.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Partner Organisation: Schweizerischer Nationalfonds (SNF)
• Cooperation Partner: Professor Dr.-Ing. Rolf Dach