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Interference measurements of the Nummela standard baseline in 2005 and 2007 / Jorma Jokela (2010)

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Titre :	Interference measurements of the Nummela standard baseline in 2005 and 2007
Type de document :	Monographie
Auteurs :	Jorma Jokela, Auteur ; P. Häkli, Auteur
Editeur :	Helsinki : Finnish Geodetic Institute FGI
Année de publication :	2010
Collection :	Publications of the Finnish Geodetic Institute, ISSN 0085-6932 num. 144
Importance :	90 p.
Format :	21 x 30 cm
ISBN/ISSN/EAN :	978-951-711-283-3
Note générale :	Bibliographie
Langues :	Anglais (eng)
Descripteur :	[Vedettes matières IGN] Géodésie [Termes IGN] comparateur de Vaisala [Termes IGN] Finlande [Termes IGN] interférence [Termes IGN] ligne de base [Termes IGN] mesurage électronique de distances
Résumé :	(Auteur) The Nummela Standard Baseline of the Finnish Geodetic Institute is a unique national and international measurement standard for length measurements in geodesy. The design of the 864-m baseline was originally, in 1933, fitted for the calibration of 24-m invar wires to determine a uniform scale for triangulation. Since 1947, the baseline has been regularly measured with the Vaisala interference comparator. As a continuation to the impressive time series, the performance and results of the latest interference measurements in 2005 and 2007 are presented in detail in this publication. Two consecutive measurements within a short time span were necessary, since only half of the baseline could be measured in 2005, due to unfavourable weather conditions. The new results again confirm the excellent stability and unique accuracy, 9xlO"8, of the baseline. The 6-pillar baseline now serves in the calibration, testing and validation of electronic distance measurement (EDM) instruments for precise surveying and mapping and in scale transfer measurements to other geodetic baselines, test fields and local geodynamical networks. The measurements are metrologically traceable to the definition of the metre through a quartz gauge system. This publication provides a summary of the rare measurement method and is a detailed supplement to the previously published or internal instruction manuals. First, we present the quartz gauge systems, which determine the scale in the Vaisala interference comparator. After a description of the present comparison method for the quartz gauges, the computation of the scale for the latest interference measurements is presented. For the interference measurements, the comparator must be separately constructed for every baseline. We describe the preparations and installations for this, followed by the observation and computation procedures. The abundant illustrations clarify the many stages. For further utilization of the baseline, the projection measurements are an essential part of the entire measurement. They transfer the distances between the mirror surfaces in the comparator to the distances between the permanently fixed transferring bars on the observation pillars, and, finally, to the baseline lengths between the underground benchmarks. We present the estimation of the uncertainty of measurement as standard and expanded uncertainties, combining all of the sources of the uncertainty in the traceability chain. The standard uncertainties of the new results range from ±0.02 mm to ±0.07 mm for the lengths of the baseline sections ranging from 24 m to 864 m. The result for the length of the entire baseline, 864 122.86 mm ±0.07 mm, differs +0.11 mm from the previous result in 1996 and +0.08 mm from the first result in 1947. The largest difference between the results in 2005 and 2007 is -0.08 mm. The state-of-the-art Nummela Standard Baseline remains a world-class measurement standard of geodetic length metrology.
Note de contenu :	1 Introduction 2 Landmarks in the history of the Nummela Standard Baseline 2.1 First international recognitions 2.2 Change from invar wires to EDM instruments as transfer standards 2.3 Recent construction works 2.4 Importance in the 2010s 3 Traceability chain of geodetic length measurements 4 Quartz gauges in the determination of the scale 4.1 Review of quartz gauge systems at Tuorla Observatory 4.2 Comparisons at Tuorla Observatory 4.3 Determination of the length of quartz gauge no. VIII in BTM00 5 Preparing the baseline for interference measurements 5.1 Principle of the Vaisala interference comparator 5.2 Preparing the observation pillars for interference measurements 5.3 Precise levellings - start of the measurements 5.4 Aligning the mirrors 5.5 Setting the mirrors at correct positions in the baseline direction 5.6 Installing the transferring bars onto the observation pillars 5.7 Installations on the telescope pillar 5.8 Installations on pillars 0 and 1 6 Interference observations 6.1 Observation procedure 6.2 About weather conditions 6.3 Personnel 7 Determination of corrections 7.1 Compensator corrections 7.2 Refraction correction 7.3 Corrections due to mirrors 7.4 Geometric corrections 7.5 Projection corrections 8 Computation of baseline lengths 8.1 Computation of the actual length of the quartz gauge 8.2 Results from interference observations in 2005 8.3 Results from interference observations in 2007 8.4 Final lengths 9 Estimation of uncertainty of measurement 9.1 Combined uncertainty of the lengths between the underground markers 9.2 Some supplementary analysis of uncertainty of measurement 10 Summary and conclusions
Numéro de notice :	14650
Affiliation des auteurs :	non IGN
Thématique :	POSITIONNEMENT
Nature :	Monographie
En ligne :	https://www.maanmittauslaitos.fi/sites/maanmittauslaitos.fi/files/fgi/FGI_Publ_1 [...]
Format de la ressource électronique :	URL
Permalink :	https://documentation.ensg.eu/index.php?lvl=notice_display&id=62678

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