The EUREF Permanent Network Densification is a collaborative effort of 26 European GNSS analysis centers providing series of daily or weekly station position estimates of dense national and regional GNSS networks, in order to combine them into one homogenized set of station positions and velocities. During the combination, the station meta-data, including station names, DOMES numbers, and position offset definitions were carefully homogenized, position outliers were efficiently eliminated, and the results were cross-checked for any remaining inconsistencies. The results cover the period from March 1999 to January 2017 (GPS week 1000-1933) and include 31 networks with positions and velocities for 3192 stations, well covering Europe. The positions and velocities are expressed in ITRF2014 and ETRF2014 reference frames based on the Minimum Constraint approach using a selected set of ITRF2014 reference stations. The position alignment with the ITRF2014 is at the level of 1.5, 1.2, and 3.2 mm RMS for the East, North, Up components, respectively, while the velocity RMS values are 0.17, 0.14, and 0.38 mm/year for the East, North, and Up components, respectively. The high quality of the combined solution is also reflected by the 1.1, 1.1, and 3.5 mm weighted RMS values for the East, North, and Up components, respectively.
The Nordic Geodetic Commission (NKG) has launched a joint NKG GNSS Analysis Centre that aims to routinely produce high qualityGNSS solutions for the common needs of the NKG and the Nordic and Baltic countries. A consistent and densified velocity field is needed for the constraining of the gla-cial isostatic adjustment (GIA) modelling that is a key component of maintaining the national reference frame realisations in the area. We described the methods of the NKG GNSS Analysis Centre including the defined processing setup for the local analysis centres (LAC) and for the combination centres.We analysed the results of the first 2.5 years (2014.5-2016). The results showed that different subnets were consistent with the combined solution within 1-2 mm level. We observed the so called network effect affecting our reference frame alignment. However, the accuracy of the reference frame alignment was on a few millimetre level in the area of the main interest (Nordic and Baltic Countries). TheNKGGNSS AC was declared fully operational in April 2017.
The Central European GNSS Research Network (CEGRN) collects GNSS data since 1994 from contributors which today include 42 Institutions in 33 Countries. CEGRN returns a dataset of coordinates and velocities computed according to international standards and the most recent processing procedures and recommendations. We provide a dataset of 1229 positions and velocities resulting from 3 or more repetitions of coordinate measurements of each site over 4 or more years. The velocity data result from a combination of eight multiyear, partially overlapping networks, using 234 stations of class A of the European Permanent Network (EPN) for alignment to the ‘European Fixed’ ETRF2000 Reference Frame. The rms (root mean square) of the 8 individual contributions to the combined solution, after a 7 – parameter Helmert transformation, is less than 5 mm in the observation period 1996–2017. This combined CEGRN network maintains the origin coincident with that of the ETRF2000 reference frame to within 1.8 mm rms for the entire period of analysis. The mean positions and velocities of common EPN Class A and CEGRN stations differ by 0.0 ± 1.1, 0.5 ± 1.0 and 0.1 ± 2.7 mm for the coordinates and 0.06 ± 0.13, -0.07 ± 0.12, 0.38 ± 0.28 mm/yr for the velocities respectively for the North, East and Up components at epoch 2010.0.
A unified and continuous national vertical network is the back-bone for geodesy, cartography, civil engineering and global positioning. International institutions are working to reach homogenous and unified vertical datum all around the globe. Levelling evaluation on the border between Latvia and Lithuania is of particular interest. Connection between vertical networks is made in three places, so connecting lines construct the two first order levelling loops. A joined loop adjustment produces a good basis for analysis and evaluation of height connection between Latvia and Lithuania not only as neighbouring countries but also as parties to the EVRS.
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