VLBI Analysis with the Multi-Technique Software GEOSAT

GEOSAT is a multi-technique geodetic analysis software developed at Forsvarets Forsknings Institutt (Norwegian defense research establishment). The Norwegian Mapping Authority has now installed the software and has, together with Forsvarets Forsknings Institutt, adapted the software to deliver datum-free normal equation systems in SINEX format. The goal is to be accepted as an IVS Associate Analysis Center and to provide contributions to the IVS EOP combination on a routine basis. GEOSAT is based on an upper diagonal factorized Kalman filter which allows estimation of time variable parameters like the troposphere and clocks as stochastic parameters. The tropospheric delays in various directions are mapped to tropospheric zenith delay using ray-tracing. Meteorological data from ECMWF with a resolution of six hours is used to perform the ray-tracing which depends both on elevation and azimuth. Other models are following the IERS and IVS conventions. The Norwegian Mapping Authority has submitted test SINEX files produced with GEOSAT to IVS. The results have been compared with the existing IVS combined products. In this paper the outcome of these comparisons is presented

A GNSS velocity field for geophysical applications in Fennoscandia

In Fennoscandia, tectonics, Glacial Isostatic Adjustment (GIA), and climatic changes cause ongoing crustal deformation of some millimetres per year, both vertically and horizontally. These displacements of the Earth can be measured to a high degree of precision using a Global Navigation Satellite System (GNSS). Since about three decades, this is the major goal of the Baseline Inferences for Fennoscandian Rebound, Sea-level, and Tectonics (BIFROST) project. We present a new velocity field for an extended BIFROST GNSS network in the ITRF2008 reference frame making use of the GNSS processing package GPS Analysis Software of MIT (GAMIT). Compared to earlier publications, we have almost doubled the number of stations in our analysis and increased the observation time span, thereby avoiding the early years of the network with many instrument changes. We also provide modelled vertical deformation rates from contributing processes, i.e. elastic deformation due to global atmospheric and non-tidal ocean loading, ice mass and hydrological changes as well as GIA. These values for the vertical component can be used for removal of these contributions so that the residual uplift signal can be further analysed, e.g., in the context of local or regional deformation processes or large-scale but low-magnitude geodynamics. The velocity field has an uplift maximum of 10.3 mm/yr in northern Sweden west of the Gulf of Bothnia and subsidence exceeding 1 mm/yr in northern Central Europe. The horizontal velocity field is dominated by plate motion of more than 20.0 mm/yr from south-west to north-east. The elastic uplift signal sums up to 0.7–0.8 mm/yr for most stations in Northern Europe. Hence, the maximum uplift related to the past glaciation is ca. 9.6 mm/yr. The residual uplift signal after removal of the elastic and GIA contribution may point to possible improvements of the GIA model, but may also indicate regional tectonic and erosional processes as well as local deformation effects. We show an example of such residual signal discussing potential areas of interest for further studies

Realising of ETRS89 as the National reference frame in Norway - EUREF89 : Vzpostavitev ETRS89 kot državnega referenčnega sestava na Norveškem - EUREF89

The introduction to a new geodetic reference frame EUREF89 in Norway is described. The further steps for a complete transition of data bases from the old system, Norwegian system, to the new EUREF89 arealso briefly described. A status for the transition to EUREF89 in Norway is also given

Next generation network real-time kinematic interpolation segment to improve the user accuracy

This paper demonstrates that automatic selection of the right interpolation/smoothing method in a GNSS-based network realtime kinematic (NRTK) interpolation segment can improve the accuracy of the rover position estimates and also the processing time in the NRTK processing center. The methods discussed and investigated are inverse distance weighting (IDW); bilinear and bicubic spline interpolation; kriging interpolation; thin-plate splines; and numerical approximation methods for spatial processes. The methods are implemented and tested using GNSS data from reference stations in the Norwegian network RTK service called CPOS.Data sets with an average baseline between reference stations of 60–70 kmwere selected. 12 prediction locations were used to analyze the performance of the interpolation methods by computing and comparing different measures of the goodness of fit such as the root mean square error (RMSE), mean square error, and mean absolute error, and also the computation time was compared. Results of the tests show that ordinary kriging with theMat´ern covariance function clearly provides the best results. The thin-plate spline provides the second best results of the methods selected and with the test data used

Estimation of Scintillation Indices: A Novel Approach Based on Local Kernel Regression Methods

We present a comparative study of computational methods for estimation of ionospheric scintillation indices. First, we review the conventional approaches based on Fourier transformation and low-pass/high-pass frequency filtration. Next, we introduce a novel method based on nonparametric local regression with bias Corrected Akaike Information Criteria (AICC). All methods are then applied to data from the Norwegian Regional Ionospheric Scintillation Network (NRISN), which is shown to be dominated by phase scintillation and not amplitude scintillation. We find that all methods provide highly correlated results, demonstrating the validity of the new approach to this problem. All methods are shown to be very sensitive to filter characteristics and the averaging interval. Finally, we find that the new method is more robust to discontinuous phase observations than conventional methods