| 1. |
- Engfeldt, Andreas, et al.
(författare)
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RG 2000 – the New Gravity Reference Frame of Sweden
- 2019
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Ingår i: Geophysica. - : Geophysical Society of Finland. - 0367-4231 .- 2324-0741. ; 54:1, s. 69-92
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Tidskriftsartikel (refereegranskat)abstract
- The increased need for improved geoid models for Global Navigation Satellite Systems (GNSS) height determination calls for additional gravity observations and quality assurance of existing data. In this perspective, a modern gravity system and the renovation of an already existing high order gravity network is considered as a moderate strategic investment which provides a firm foundation for further activities. Here the new gravity reference frame RG 2000 for Sweden is presented. RG 2000 is realized by absolute gravity observations at 109 stations. The absolute points are connected via old and new relative gravity observations, including another 216 points. Points and observations have been chosen so that good overlap with the older Swedish reference frames, RG 62 and RG 82, is achieved, allowing to evaluate the older frames and transformations between them. RG 2000 is based on a zero permanent tide system with epoch 2000.
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| 2. |
- Vestøl, Olav, et al.
(författare)
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NKG2016LU: a new land uplift model for Fennoscandia and the Baltic Region
- 2019
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Ingår i: Journal of Geodesy. - : Springer. - 0949-7714 .- 1432-1394. ; 93:9, s. 1759-1779
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Tidskriftsartikel (refereegranskat)abstract
- We present the official land uplift model NKG2016LU of the Nordic Commission of Geodesy (NKG) for northern Europe. The model was released in 2016 and covers an area from 49° to 75° latitude and 0° to 50° longitude. It shows a maximum absolute uplift of 10.3 mm/a near the city of Umeå in northern Sweden and a zero-line that follows the shores of Germany and Poland. The model replaces the NKG2005LU model from 2005. Since then, we have collected more data in the core areas of NKG2005LU, specifically in Norway, Sweden, Denmark and Finland, and included observations from the Baltic countries as well. Additionally, we have derived an underlying geophysical glacial isostatic adjustment (GIA) model within NKG as an integrated part of the NKG2016LU project. A major challenge is to estimate a realistic uncertainty grid for the model. We show how the errors in the observations and the underlying GIA model propagate through the calculations to the final uplift model. We find a standard error better than 0.25 mm/a for most of the area covered by precise levelling or uplift rates from Continuously Operating Reference Stations and up to 0.7 mm/a outside this area. As a check, we show that two different methods give approximately the same uncertainty estimates. We also estimate changes in the geoid and derive an alternative uplift model referring to this rising geoid. Using this latter model, the maximum uplift in Umeå reduces from 10.3 to 9.6 mm/a and with a similar reduction ratio elsewhere. When we compare this new NKG2016LU with the former NKG2005LU, we find the largest differences where the GIA model has the strongest influence, i.e. outside the area of geodetic observation. Here, the new model gives from − 3 to 4 mm/a larger values. Within the observation area, similar differences reach − 1.5 mm/a at the northernmost part of Norway and − 1.0 mm/a at the north-western coast of Denmark, but generally within the range of − 0.5 to 0.5 mm/a.
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| 3. |
- Nilfouroushan, Faramarz, 1968-, et al.
(författare)
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Evaluation of newly installed SWEPOS mast stations, individual vs. type PCV antenna models and comparison with pillar stations
- 2016
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Ingår i: Geophysical Research Abstracts. - Vienna : European Geosciences Union.
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Konferensbidrag (refereegranskat)abstract
- For about two decades, SWEPOS (the Swedish Permanent GNSS network) pillar stations have been used indifferent geodetic and geodynamic studies. To keep continuous measurements of these long lived pillar stationsand at the same time modernizing the SWEPOS network, it has been decided to install new truss mast stations,equipped with modern and individually calibrated antennas and radomes, capable of tracking all new GNSSsatellites. Installation of mast stations started in 2011. Today, each pillar station in the SWEPOS permanent GNSSnetwork has a close-by truss mast station, mostly in 10 meters distance with individual calibrated Leica chokering antenna and its attachment (LEIAR25.R3, LEIT). Due to their closeness to pillars, the modern mast stationsmay provide additional information for the analysis of ground movements in Sweden e.g. to distinguish betweentectonic and geodynamic processes (e.g. land uplift in Sweden).In this study, we have used two datasets from two different seasons for 21 pillars and 21 mast stations andformed different networks. The mast network has been processed using both IGS standard (type) and individuallycalibrated PCV (Phase Center Variation) models and therefore the effect of these two different PCV models onheight components has been investigated. In a combined network, we processed all 42 stations (21 pillars+21mast) to see how this multi-baseline network (861 baselines) combination differs from independent mast or pillarnetworks with much less baselines (210 baselines). For our analysis, we used the GAMIT-GLOBK softwareand compared different networks. Ambiguity resolutions, daily coordinate repeatability and differences betweenheight components in different solutions are presented. Moreover, the GAMIT and BERNESE solutions forcombined mast and pillar networks are compared.Our results suggest that the SWEPOS truss mast stations can reliably be used for crustal deformation studies.The comparison between pillar and mast stations shows similar time series for different horizontal and verticalcomponents and their Normalized rms (nrms) and weighted rms (wmrs) are almost equal.Comparison of standard and calibrated PCV models for mast stations show notable differences in height compo-nents and reach up to14 mm. These differences are antenna-dependent and are not systematic offsets. Therefore,whenever available, individual calibrated antenna models have to be used instead of standard (type) calibratedmodels.This study is part of the Swedish CLOSE III research project between Lantmäteriet, SP, and Chalmers Universityof Technology.
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