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GEODEETTINEN LAITOS |
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14.01.2003 kirjasto@fgi.fi |
SUOMEN GEODEETTISEN LAITOKSEN JULKAISUJA |
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| GEODETIC DATUMS, REFERENCE SYSTEMS AND GEODETIC NETWORKS IN ESTONIA by Rüdja, Andres Abstract The triangulation networks and the terrestrial datums established in Estonia during the period from 1816 up to 1991 are investigated. The precision estimation based on inner consistency of measurements is shown. According to the Concept, worked out in 1995 . 1996, the data from traditional measurement techniques together with GPS will be used in determination of changes in space and time, for unification of vertical reference systems, determination of geoid models, etc. Conditions including the location of local deformation areas, soil characteristics, buried ancient valleys, faults in sedimentary bedrock and basement, block structure of the bedrock etc for establishment of the national geodetic network in Estonia are wor- ked out. To make the realisation of ideas feasible an extensive material is collected and combined. Due to the integrated character of the network the benchmark const- ruction is designed to be comparable in stability with the ground benchmarks used in the I order levelling. The GPS campaign with the aim to verify the results of the EUREF BAL92 cam- paign and to investigate the site-specific error sources was planned and held in 1994. The data was processed with Bernese GPS Software in 1994 . 1995. The site-specific error sources are studied. The measurement technologies of the I and II order space geodetic networks in Estonia are described. A new ETRS89 realisation was carried out within the EUREF-Estonia-1997 project when the I order network consisting of 13 points was measured. The data was evaluated with Bernese GPS Software in 1998. According to the resolution of the EUREF Prague Symposium in 1999, the results of the given project corresponded to class B, i.e. about ±1 cm at the epoch of observa- tion. Seven I order points were endorsed as improvements and extensions of EUREF89. The II order National Geodetic Network consisting of 199 points with the average distance between adjacent points 15 km was measured in 1997. The data was evaluated with Bernese GPS Software in 1998. Our solution for the Densification Network is described, which strikes a balance between, on the one hand, the impact of the ionospheric refraction in case of L1 only, and on the other hand, the increase of noise level accompanying the introduction of linear combinations of GPS signals. The changing accuracy characteristics during the last Solar Cycle based on the measured 15 692 GPS vectors of the Densification Net- work of Estonia are outlined. The results of comparison of GPS vectors with the re- sults from precise EDM measurement are shown. The joint adjustment of the indivi- dual Densification Network areas consisting of 15 673 vectors and 3922 points perfor- med in 2001 is described. The results of the similarity transformation between the ETRS89 realisation in Estonia and two latest historical datums extended over the whole of Estonia, i.e., the 1937 datum and the Pulkovo 1942 datum are shown. |
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27.09.2004kirjasto@fgi.fi |
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| Geodeettinen laitos Geodeetinrinne 2, PL 15 02431 MASALA |
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: (09) 2955 50