generally use the laser scanner for many different applications and still on areas such as medium-scale landslides, landfills and quarries. The project under consideration is rather consisted in verifying the change of the crack of some houses as a mirror of the evolution of a widespread collapse in a town in Lombardy. Since the project is currently still in progress, I will confine myself to the description of volunteer activities and omit the names of places.
However, this town of Lombardy is characterized by a collapse to a circumscribed area of \u200b\u200bthe municipality particularly karstified. In these places has risen a not insignificant number of homes that, over time have begun to express widespread subsidence, inclinations of the walls (even those carriers) is also very deep cracks that often have eroded structures. For obvious reasons the council was unable to intervene directly on private properties and for this reason it was decided to implement a particular action on soil protection and avant-garde: the excavation a series of trenches along the roads of the country from which to depart a series of micro orizzonatli radial on which the houses could take the weight off. Far be it from me on assessments about the quality of the project (not my job) I was still asked if it was possible to make assessments (in fact non-partisan in conjunction with the geotechnical monitoring conducted by the firm in charge of piling) on \u200b\u200bthe move recorded from the homes during the excavations and in the aftermath of the regional planning. My monitoring proposal was to make three campaign tracking laser scanner from the ground.
The first campaign has in fact given the initial crack pattern (I think I may have devastating but accurate idea of \u200b\u200bthe house too!). Then, after six months I have made, on the same houses and the same points of taking a new set of scans. The quality and detail of the scans was a very dense number of points, in order to obtain a realistic picture of great detail and also those cracks millimeter. Following the scans I have since carried out the photos with the built-in laser fotocmera. The defenses of processing (carried out by the JRC 3D Reconstructor - http://www.gexcel.it/ ) consisted initially in the town of referencing in all scans and all images to create three-dimensional models are similar or totally overlapping for the two sets of scans. Then I made two types of test: the automatic inspection of the two meshes (triangulations of automated comparison of point clouds) to produce a guideline with regard to areas where the clouds of points were not perfectly overlapping. The problem, however, as a result of this development was born when the reliability dell'inspection is in fact an order of magnitude as the size of the change in open fractures that I expected. Result: it is true that in some cases the inspection marks a change in me, but that variation can be even within intrinsic error of measurement, or alternatively if the inspection marks nothing I can also not see anything related to the fact that changes in position are numerically inferior to the definition of the scan or the inspection itself. How to work then? In this sense, the literature, and also the excellent editing programs I have come to meet. It 's possible to create digital orthophotos of my scans orthometric just putting themselves in position, and in particular made the mesh (triangulation of the scan) and those with digital photos (thus obtaining a three-dimensional pictures) for both series may be obtained by the Broadcasting orthophotos of the first set and second set. Through the program Kubit ( http://www.gexcel.it/ ) was then possible to export each of the digital orthophotos and replace my object in different levels: level ortho first scan, second scan ortho level, the crack level 1 (derived from copying by hand in each of the slots of the first set of scans) and at the crack 2 (obtained in the same way.) After this operation, the result is a possible comparison of crack patterns of the two series of scans at all points where I proceeded to detect the cracks.
results. Areas of variation of the crack corresponding to those too superficially by automatic inspection in Recostructor (index of this good product quality information), in particular, it was possible to verify a substantial change of the crack in terms of number of cracks per unit area for extension of the cracks themselves. The major fissures in fact have increased their presence and longitudinal data, while smaller ones have generally retained their extension.
The data were then supported by those of fessurimetri.
Reflection. The fessurimetri are a very reliable and also permit the continuous monitoring of the cracks, the limit of the use of fessurimetri however, is that if a new slot opens to two centimeters from the old one and also with a size of 50 cm the fessurimetro does not realize it. Hence the validity of the laser scanner data in these conditions. Obviously the costs are different in terms of time and effort although still in a telemetry system for a number of cracks even half of those observed with the laser results with fessurimetri certainly more costly.
Thoughts?
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