Investigation of the use of Laser Scanning for Deformation Monitoring

Abstract: The ability of fast and accurate acquiring of large 3D spatial data is the main benefit for consideration of a terrestrial laser scanner in deformation monitoring. The objective of this paper is to discuss this technique with support of practical experiments performed inside a laboratory. It also includes measuring changes from millimetre to sub millimetre level and a comparison of measurements from a terrestrial laser scanner with measurements of other instruments. Various areas of applications are reviewed. The report discusses a surface modeling method to estimate deformation parameters of objects, such as planar, spherical and cylindrical surface representations. Illustrative numerical examples are performed by simulating randomly generated sample point coordinates for estimation of changes of modeled planar and cylindrical surfaces. The practical experiments were performed using a scan of a carton box, a ball and a rounded paper holder, which correspond to the planar, spherical and cylindrical surfaces, respectively. Independent measurements were performed using a total station and a measuring tape to make a comparison with the scanner measurements. A statistical test was performed independently for the changes obtained from each type of modeled surface in order to check whether the movement is real or due to measurement noises.  A significant change of the normal of a plane was detected between epochs, and similar results were obtained from both scanner and total station measurements. The normal of the plane was rotated by  between scan epochs. A translation of 3.2 and 3.7 millimetres were detected between scan epochs for the center of the sphere and axis of the cylinder, respectively. Only the scanner data was used in this case. From the scanner measurement changes in radii of the sphere and the cylinder were obtained as 1.6 and 3.1 millimetres, respectively between scan epochs. The measurement of the scanner was verified by performing independent measurements using measuring tape. And hence the change in radii of the sphere and the cylinder were obtained as 2.5 and 4 millimetres, respectively.