A Global Geodetic Reference Frame (GGRF) is a fundamental requirement to relate measurements taken from anywhere on the Earth. It provides the basis on which a broad spectrum of scientific and industrial applications rely, and is crucial in any field where precise location information is necessary, including monitoring climate change, agriculture, and changes in groundwater.

The working group Satellite Geodesy at the Institute of Geodesy (IFG), Graz University of Technology (TUG) provide a wide range of of products which are processed and published to the international community such as gravity field ans mass transport solutions, Precise Orbit Data (POD) of Low Earth Orbit (LEO) satellites and Global Navigation Satellite Systems (GNSS) station networks and much more. The products are utilized by various organizations, such as the International Combination Service for Time-variable Gravity Fields (COST-G) of the International Association of Geodesy (IAG), the International GNSS Service (IGS) or the European Copernicus POD Service Quality Working Group (CPOD). A consistent and accurate GGRF is the foundation of all our products and, as such, is essential to ensure the quality of our in-house computed products.

A GGRF is established and maintained by an international community, culminating in the International Terrestrial Reference Frames (ITRF). The latest version, ITRF2020, is based on four space geodetic techniques: GNSS, VLBI, SLR and DORIS. During the process of combining the four space geodetic solutions, discrepancies required compromises in the ITRF2020 solution. The geocenter follows only the SLR technique, while the scale is fixed only by the SLR and VLBI solutions. Although GNSS has the capability to estimate both, it was excluded from the compromises in these areas as GNSS was considered inaccurate in both cases. Therefore, in this project we aim to improve the in-house GNSS reference frame processing to provide a more consistent estimate within our software GROOPS. To achieve this, we aim to adapt the GNSS Frame Estimation process to estimate the geocenter and improve the scale estimation by using more sophisticated antenna calibration models. The incorporated changes to the GNSS reference frame estimation are evaluated on 10 years of daily results based on a selected multi-GNSS station network.