Following Resolution 1 of the EUREF 2008 symposium in Brussels, the Time Series Special Project was discontinued and integrated in the routine EPN operations, see Products > Time Series Analysis.

Introduction

The EPN has been established in 1996 with the primary goal to support the maintenance and the continuous improvement of the European Terrestrial Reference System (ETRS89) and its successive realizations. Although the EPN was primarily designed for reference frame maintenance, it became a valuable tool for the understanding of the present-day geokinematics within Europe and its adjacent areas. The EPN Coordinate Time Series Analysis Special Project (TSA_SP) has been established in 2001 and it is considered as the interface between geodesists and geophysicists; it strengthens the EPN as a geodetic reference network and simultaneously also provides high quality kinematic information for geophysics. The TSA_SP's main study area is the EPN, but the project members also focus on specific regions with denser station distribution.

Activities and products

The basic activity of the TSA_SP is the routine monitoring of the EPN station coordinates in order to ensure the long-term reliability of the EPN network and its products.
The TSA_SP uses the weekly combined EPN SINEX solutions - created by the EPN Combination Centre at BKG - as input for the estimation of coordinates and velocities for each of the EPN stations. These estimations are obtained after a rigorous cleaning of station coordinates outliers. In addition, a new station position is estimated when an equipment change causes a jump in the station coordinates. The uncertainties of the estimated coordinates and velocities mainly depends on the duration of the station observation period. However, since most GNSS analysis and combination software incorrectly assumes that only white noise is present in the geodetic time series, these uncertainties are considerable over-optimistic and consequently unrealistic. To derive more realistic coordinate and velocity uncertainties, the TSA_SP determines the true noise model and uses this model for the determination of the uncertainties.

Summarized, the main results and products of the TSA_SP are:

1. The computation of the EPN TSA_SP multi-year (or cumulative) solution resulting in : cleaned time series plots, a catalogue with the station coordinates and velocities, and a catalogue with the coordinate offsets and outliers
2. The determination of realistic coordinate and velocity uncertainties by estimating the spectral index of the noise of the coordinate time series
3. The harmonic analysis of the coordinate time series by estimating the seasonal periodic term and providing de-trended, cleaned time series plots
4. Three types of CLEANED time series plots available from the EPN CB:
   • Type 1: Cleaned series, where the tilt of the coordinate development fully corresponds to the ETRF2005 velocity. The estimated velocities and the respective uncertainities [unit is cm/year] are displayed at the bottom of the plots.
   • Type 2: De-trended cleaned series, where the estimated annual periodic signal is displayed for each components and the estimated amplitude [mm] and phase lag [degree] values are shown at the bottom of the plot.
   • Type 3: De-trended cleaned series, where the annual term is removed, but the estimated sinusoidal signal is still displayed.
For each of them, the coordinate outliers have been removed and a set of new coordinates has been estimated when an equipment change caused a discontinuity in the station coordinates. Both of them are indicated on the plots using lines of different colors.
5. Case studies

Project members

A. Kenyeres  Chairman	FOMI Satellite Geodetic Observatory, Hungary
J. Hefty	Slovak Technical University, Bratislava (SUT)
A. Caporalli	University of Padova (UPA), Italy
L. Ferraro	Agenzia Spaziale Italiana (ASI), Italy
L. Jivall	National Land Survey of Sweden (NLS), Sweden
M. Poutanen	Finnish Geodetic Institute (FGI), Finland
R. Fernandes	DEOS(DEO), The Netherlands - Portugal
A.J.M. Kosters	Meetkundige Dienst of Rijkswaterstaat, The Netherlands
G. Stangl	Observatorium Lustbuehel, Graz (OLG), Austria
J. Bosy	Agricultural University Wroclaw (AUW), Poland
C. Bruyninx	Royal Observatory of Belgium (ROB), Belgium
E. Brockmann	Swiss Federal Office of Topography (LPT), Switzerland
N. Panafidina	Institute of Applied Astronomy (IAA), Russia