DBPapers
DOI: 10.5593/SGEM2014/B22/S9.011

ASSESSMENT OF SUITABILITY OF TERRESTRIAL LASER SCANNING FOR DETERMINING DISPLACEMENTS OF COFFERDAM DURING MODERNIZATION WORKS ON THE REDZIN SLUICE

Z. Muszynski
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-11-7 / ISSN 1314-2704, June 19-25, 2014, Book 2, Vol. 2, 81-88 pp

ABSTRACT
In recent years the use of terrestrial laser scanning has become wider in engineering geodesy. At the same time, the accuracy of laser scanners has increased significantly. The author found it worth considering, however, if the scanner accuracy is sufficient for precise measurements of the displacement of engineering structures. It is not without significance what type of structure is subject to analysis and what are the conditions in which the survey is being performed. This paper presents the assessment of suitability of terrestrial laser scanning for determining horizontal displacement of the cofferdam structure. The particular cofferdam included in this case study was made of sheet pile walls to serve as a temporary partition during the modernization works on the Rędzin sluice, located on the Oder River in the south-western part of Poland. In the research phase, an initial survey and a few periodic surveys were performed. The measurements of the cofferdam’s horizontal displacements were taken on non-stabilized instrument stations in relation to external reference points. Most of the scanner measurements were carried out in challenging conditions, e.g. unfavorable angles of the laser beam reflection, wet and rusty surface of the sheet pile wall, or a large number of obstacles which cast shadow on the cloud of points. For the purpose of research, independent surveys of horizontal displacement values were made using a high-precision motorized total station. The least squares method was used in order to process the data collected through survey. Subsequently, the results obtained both from the scanner and from the total station were compared. The analysis included the position of the check points at different times of the survey, after which the deviation of the values of horizontal displacement could be determined. On that basis, it was possible to make an assessment of the scanner accuracy for displacement measurements. The final part of the paper summarizes the results, and the conclusions take the form of several recommendations useful in the engineering practice.

Keywords: sluice, terrestrial laser scanning, total station, horizontal displacements