Densification of the ITRF2014 position and velocity solution in the Nordic and Baltic countries

Abstract

The growing need for a consistent and densified GNSS position and velocity solution for the Nordic and Baltic countries resulted in development of the joint GNSS Analysis Centre of the Nordic Geodetic Commission (NKG) in 2012. We first developed the methods of the operational processing and combination of solutions and then reprocessed the full data history between 1997 and 2017. In this study, we present an ITRF2014 densification for the area including 252 stations having more than 3 years of data. We combined all 20 years of daily solutions with full covariance matrices instead of station-wise analysis and analyzed the noise characteristics of the residual time series. We concluded that the flicker plus white noise uncertainty estimates were more robust than the general power-law estimates. Additionally, we found significant horizontal velocity differences at the co-located stations, pointing out biases not included in the formal uncertainties. The solution is more accurate and denser than any previous estimate, and it will be of great benefit for maintaining the reference frames in the Nordic and Baltic countries, as well as for the geodynamic studies in the area.

Past and Future Sea Level Changes and Land Uplift in the Baltic Sea Seen by Geodetic Observations

“…The GNSS uplift values used in the present study were the trends from the NKG Analysis Centre solution by Lahtinen et al (2019). There were altogether eight stations in the study area, one in Finland and seven in Sweden.…”

“…The Vaasa station has previously shown some anomalistic low GNSS-derived rates (Kierulf et al 2014;Lidberg et al 2009), which has now been addressed to changing surroundings of the station. For the Lahtinen et al (2019) result the time series has been modified more drastically and fits now the overall picture better. The absolute gravity value of Vaasa AA is somewhat higher than expected.…”

“…The GNSS dominated weighted mean values have clearly lower uncertainty than the land uplift model, whereas the other techniques' uncertainties are two of threefold. The uncertainty of GNSS time series has been studied a lot and it has been suggested that the true uncertainty might be in the order of 0.2-0.3 mm/year (Lahtinen et al 2019). This requires still more investigation.…”

Forty-three years of absolute gravity observations of the Fennoscandian postglacial rebound in Finland

“…Using the very long time series, we will look at the time needed for gravity trends to stabilize over time. Then, we will use the gravity trends that have shown to be stable in time to study the relationship between gravity rates and uplift rates, not only from the semi-empirical land uplift model, but also from GNSS time series, including the most recent GNSS solution from Lahtinen et al (2019). The new ratios between gravity rates and uplift rates we present will give new input for future GIA studies.…”

“…Due to the disappearance of past ice loads, the Earth's crust is continuously rising, causing vertical velocities up to 1 cm/yr in Fennoscandia (Milne et al 2001). This postglacial rebound (PGR) process has been extensively studied with a variety of techniques, such as tide gauges (Ekman 1996), repeated precise levelling (Mäkinen and Saaranen 1998) and continuous observations using global navigation satellite systems (GNSSs) (Johansson et al 2002;Kierulf et al 2014;Lahtinen et al 2019). Contemporary uplift rates determined by these techniques are used to constrain geophysical models of GIA (e.g.…”