Abstract
Abstract. Laser scanning is now a common technology in the surveying and monitoring of large engineering infrastructures, such as tunnels, both in motorways and railways. Extended possibilities exist now with the mobile terrestrial laser scanning systems, which produce very large data sets that need efficient processing techniques in order to facilitate their exploitation and usability. This paper deals with the implementation of a methodology for processing and presenting 3D point clouds acquired by laser scanning in tunnels, making use of the approximately cylindrical shape of tunnels. There is a need for a 2D presentation of the 3D point clouds, in order to facilitate the inspection of important features as well as to easily obtain their spatial location. An algorithm was developed to treat automatically point clouds obtained in tunnels in order to produce rectified images that can be analysed. Tests were carried with data acquired with static and mobile Riegl laser scanning systems, by Artescan company, in highway tunnels in Portugal and Spain, with very satisfactory results. The final planar image is an alternative way of data presentation where image analysis tools can be used to analyze the laser intensity in order to detect problems in the tunnel structure.
Highlights
Laser scanning systems are an important technology in the monitoring of engineering infrastructures
Standard image processing techniques can be used for an automatic detection but it requires that surfaces are transformed onto planes in order that the data can be represented as a planar image
This paper describes an algorithm that takes a point cloud and identifies the tunnel alignment, fits curves to the cross-sections profiles and divides the tunnel in small sections, mapping it into a plane
Summary
Laser scanning systems are an important technology in the monitoring of engineering infrastructures. The deformation that will occur is very small, not degrading the International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B3, 2012 XXII ISPRS Congress, 25 August – 01 September 2012, Melbourne, Australia perception of dimensions in the rectified image of the tunnel surface This method was developed in cooperation with Artescan-3D Scanning, a Portuguese company that owns a Riegl VMX-250CS6 mobile laser scanning system (figure 2). The same is done for a point at 75% of the segment, as shown in figure 8: The aim of these two intermediate plans is to obtain the cross section of the tunnel. The cross-section is composed by all the centroids of the angular intervals (Figure 9) This stage is repeated to calculate the second section of the tunnel segment, at 75% of the distance.
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