Calibration of the BEV Geodetic Baseline (3873) |
| Jorma Jokela, Pasi Häkli (Finland), Rupert Kugler, Helmut Skorpil and Michael Matus (Austria) |
Mr. Jorma Jokela
Specialist Research Scientist, Laboratory Head
Finnish Geodetic Institute
Department of Geodesy and Geodynamics
National Standards Laboratory of Length
Finnish Geodetic Institute
PL 15 (Geodeetinrinne 2)
Masala
FI-02431
Finland
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| Corresponding author Mr. Jorma Jokela (email: jorma.jokela[at]fgi.fi, tel.: + 358 9 29555219) |
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| [ abstract ] [ paper ] [ handouts ] |
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Published on the web 2010-01-14
Received 2009-11-19 / Accepted 2010-01-14 |
| This paper is one of selection of papers published for the FIG Congress 2010 in Sydney, Australia and has undergone the FIG Peer Review Process. |
FIG Congress 2010
ISBN 978-87-90907-87-7 ISSN 2308-3441
http://www.fig.net/resources/proceedings/fig_proceedings/fig2010/index.htm
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Abstract |
| New methods for long range dimensional metrology are developed in the European Metrology Research Programme (EMRP) joint research project “Absolute long distance measurement in air”. A part of this project, bringing together nine European metrology research institutes, is the work package for validation and reproducibility estimation of new absolute distance measurement (ADM) instruments outdoor. To improve facilities for this the 1 080 metres geodetic baseline of the Austrian metrology institute BEV (Bundesamt für Eich- und Vermessungswesen) in Innsbruck was calibrated in September 2008 by transferring the scale from the Nummela Standard Baseline of the Finnish Geodetic Institute (FGI). The extremely stable 864 metres 6-pillar baseline in Finland is widely known as the most accurate geodetic baseline in the world. The length is traceable to the definition of the metre with 0.07 mm standard uncertainty through a quartz metre system and white light interference measurements with the Väisälä comparator. The scale transfer was performed using the most accurate existing electronic distance measurement (EDM) instrument as transfer standard. We present the method – as the best current practice and state-of-the-art – and results of the scale transfer to the BEV geodetic baseline.
Calibration of the transfer standard included four calibrations at Nummela before and four after the measurements in Innsbruck, altogether 240 distances. Scale correction of +0.151 mm/km was determined for the EDM instrument with 0.049 mm/km standard uncertainty. Measurements in Innsbruck included four calibrations of the 7-pillar baseline, altogether 168 distances. The observations were adjusted after velocity corrections and geometrical reductions. All the 21 slope distances 30 m – 1 080 m between observation pillars were solved with 0.21 mm to 0.77 mm extended uncertainty; 0.7 mm/km uncertainty was reached for the longest distance. In the estimation of total measurement uncertainty, the contribution of the main source, determination of velocity corrections due to weather conditions, is discussed in some detail. Stability of the baseline is proved by comparing the results with a set of previous measurements. The new traceable results of calibration of the BEV baseline are directly usable in testing and calibration of high precision EDM instruments.
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| Keywords: Standards; Positioning; Engineering survey; length metrology; geodetic baseline; traceability; measurement standard |
