Juliette Legrand

Comparison of Regional and Global GNSS Positions, Velocities and Residual Time Series

More than 10 years (1996–2008) of weekly GPS solutions of 299 globally distributed stations have been used to quantify the impact of the reference frame definition and especially the size of the network on the estimated station positions, velocities, and residual position time series. For that purpose, weekly regional solutions (covering the European region) and global solutions have been respectively stacked to obtain regional and global station positions, velocities, and residual position time series. In both cases, the estimated long-term solutions have been tied to the ITRF2005 under minimal constraints using a selected set of reference stations. This study shows that: (1) regional position and velocity solutions can present biases with respect to each other and to global solutions, while in comparison, global solutions are much more stable; (2) the obtained residual position time series are affected by the size of the network with significantly reduced periodic signals in the regional networks, e.g. a 27% reduction of the annual signals in the height component.

Erratum to: Influence of different GPS receiver antenna calibration models on geodetic positioning

In the original publication, the last five sentences of the third paragraph under the section Results were incorrectly published. The corrected text is given below. ‘‘Specifically the update of the type mean robot calibration of the TRM29659.00/NONE caused a position offset of -3.9 mm in the east component and 5.8 mm in the up component. Note that its type mean calibration in the igs08.atx is based on 18 individual calibrations compared to 12 in the igs05.atx, hence the importance of including RMS values in the IGS antenna calibration files.’’

IAG WG SC1.3 on Regional Dense Velocity Fields: First Results and Steps Ahead

The Working Group on “Regional Dense Velocity Fields” (see http://epncb.oma.be/IAG) of the International Association of Geodesy (IAG) aims at densifying the International Terrestrial Reference Frame and creating a dense velocity field based on regional and global GNSS networks. With the goal to generate a high-quality solution for a core network, several newly reprocessed global and regional cumulative position and velocity solutions were submitted to the Working Group. In order to find a consensus on discontinuity epochs for stations common to several networks (an issue which was problematic in previous submissions), the new submissions were restricted to contain only the core networks over which the analyst has full control so that ITRF2008 discontinuities could be applied. The 3D-RMS of the agreement of the new solutions with the ITRF2008 (after outlier rejection) varies between 0.6 and 1.1mm/year; it is extremely good for some solutions, while others still require more iteration to reach the required level of agreement. A part of these disagreements has been identified and often originates in the use of different data time spans within the ITRF2008 and submitted solution.