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RISS 인기검색어
- 검색키워드
- 저자 : Grzegorz Lenda (검색결과 3 건)
- 무료
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The effect of partial transparency of spherical targets on TLS point clouds registration accuracy
Grzegorz Lenda,Urszula Marmol,Michał Buczek 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7
Registering of point clouds from terrestrial laser scanning, is often carried out using spherical targets. Instead of expensive originaltargets, it is also possible to use other spherical elements. Such targets, encountered in practice, may be, for example, Styrofoamspheres, spheres built using 3D printers, spherical, milky lampshades. Most spheres which are used as substitutes, have a certaincommon feature: as a result of partial transparency of the material, the laser beam can penetrate inside, changing distancemeasurements. This applies both to glass spheres and a wide range of synthetic products. These materials may therefore have anegative effect on the accuracy of determining the centers of the reference spheres and, consequently, the accuracy of registrationpoint clouds in neighbouring scanners’ positions. This paper presents the results of the research studies allowing to assess this effect. Both the accuracy of determining the centers of the spherical targets, as well as the displacements occurring in the point cloudsmerged with their use were determined. Specialized field: Surveying & Geo-Spatial Engineering : Deformation Surveying
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Grzegorz Lenda,Marcin Ligas,Urszula Marmol 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.2
Shell structures belong to a characteristic group of objects for which it is essential to know the magnitude and distribution of localdeformations of the coat. Deformations may be important both in terms of stability, as well as special functions performed by theseobjects. While survey instruments usually ensure the required accuracy of the measurements, the methods for providing amathematical description of the shape of shells do not always allow for a correct detection of deformations. This paper comparesseveral methods of approximation potentially useful for making a precise description of the shape of a given shell object. Splinefunctions, as the most versatile tool in terms of description of objects shape, were adopted as the base method. For comparisonpurposes, according to the shape of the object in question, kriging and Fourier series methods were selected. Particular attention hasbeen paid to the accuracy aspect, which has enabled deformations to be determined within centimeter or subcentimeter accuracy. Results of the study revealed the greatest overall accuracy of spline functions. This accuracy however decreases quickly when theobservations become more irregular. Both, the past and future studies of the authors focus on integrating the best features of thedescribed methods in order to ensure a high accuracy of the created models. The results may be useful not only in surveying but alsoin other fields associated with the approximation of surfaces based on measurement data.
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The Use of Surface Interpolation Methods for Landslides Monitoring
Grzegorz Lenda,Marcin Ligas,Paulina Lewi ska,Anna Szafarczyk 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.1
The subject of this study is selection of mathematical description (interpolation method) of landslides surface for the purpose of periodic control of terrain movements. Monitoring of landslides, considered in this work, concerns points of periodic GPS or tacheometric measurements carried out in a relatively regular grid. For economic reasons, the grid usually consists of limited group of about several dozen of points that do not allow for an exact description of the terrain surface, nevertheless a general movement of a landslide can be detected (observed). Replacement of discrete set of points to a continuous surface model allows for a better assessment of the phenomenon especially within the scope of its main directions of activity. The choice of best performing interpolation method in order to construct a reliable numerical terrain model was performed through tests carried out on complex model surfaces. These model surfaces encompassed various configurations of terrain relief. In this study four interpolation methods i.e. splines, kriging triangulation with linear interpolation and IDW are compared. Tests on model surfaces distinguished the method of splines as the best performing one as well as the method of kriging which is suitable in some instances. The selected method of splines was then applied to periodically monitored landslide in Milówka in the south of Poland. Interpolation by means of splines allowed for observing progressive movements of the landslide surface with accuracy up to several millimeters. This confirms the usefulness and reliability of this method in landslides monitoring. Specialized field: Surveying & Geo-Spatial Engineering : Deformation Surveying
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