The Noise Properties and Velocities from a Time-Series of Estonian Permanent GNSS Stations

Tarmo Kall,Karin Kollo,Aive Liibusk,Tõnis Oja

doi:10.3390/geosciences9050233

Tarmo Kall, Karin Kollo + Show 2 more

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https://doi.org/10.3390/geosciences9050233

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Abstract

The aim of this study was to estimate the noise properties, velocities, and their uncertainties from a time-series of selected (~9 years long) Estonian continuously operating Global Navigation Satellite System (GNSS) stations. Two software packages based on different processing methods, Gipsy–Oasis and Bernese, were used for daily coordinate calculations. Different methods and software (Tsview, Hector, and MIDAS) were used for coordinate time-series analysis. Outliers were removed using three different strategies. Six different stochastic noise models were used for trend estimation altogether with the analysis of the noise properties of the residual time-series with Hector. Obtained velocities were compared with different land uplift and glacial isostatic adjustment models (e.g., ICE-6G (VM5a), NKG2016LU, etc.). All compared solutions showed similar fit to the compared models. It was confirmed that the best fit to the time-series residuals were with the flicker noise plus white noise model (for the North and East component) and generalized Gauss–Markov model (for Up). Velocities from MIDAS, Tsview, and Hector solutions within the same time-series (Gipsy–Oasis or Bernese) agreed well but velocity uncertainties differed up to four times. The smallest uncertainties were obtained from Tsview; the MIDAS solution produced the most conservative values. Although the East and Up component velocities between Gipsy and Bernese solutions agreed well, the North component velocities were systematically shifted.

Highlights

Glacial isostatic adjustment (GIA) is a dominant cause of the long-term intra-continental deformations and motion of the geodetic points in Estonia
Gipsy–Oasis II ver. 6.4 (GOA), outliers removed with Tsview and 3-sigma level; GOA, outliers removed with Hector and IQ-factor 2.2; GOA, outliers removed with Hector and IQ-factor 3; Bernese ver. 5.2 (BERN), outliers removed with Tsview and 3-sigma level; BERN, outliers removed with Hector and IQ-factor 2.2; BERN, outliers removed with Hector and IQ-factor 3
The Tsview three-sigma rule detected the largest number of outliers from GOA and BERN

Summary

Introduction

Glacial isostatic adjustment (GIA) is a dominant cause of the long-term intra-continental deformations and motion of the geodetic points in Estonia. Glacial isostatic adjustment-related land uplift signal in precise levelling data and tide gauge observations are quite well studied in Estonia [1,2,3,4,5]. Model NKG2016LU (Figure 1) was released by the Nordic Geodetic Commission (NKG) [10]. It combines the geodetic observations (repeated levelings and velocities of cGNSS stations) with predicted land motion from the GIA model. A joint NKG GNSS Analysis Centre has been launched by the initiative of NKG It aims to routinely produce high-quality GNSS solutions (coordinates, velocities, and their uncertainties) for the common needs of the NKG and the Nordic and Baltic countries [11]. Like GNSS, other satellite-based geodetic methods (SLR, DORIS, InSAR) have proved to provide accurate station

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