Structural monitoring. The final goal of this study is to evaluate the possibility of performing
a deformation analysis by means of TLS data. Thanks to TLS technique it is possible to acquire a
dense and accurate point cloud describing the external surface of the wall. Unfortunately, even
though different scans have been georeferenced into a stable and accurate reference system, the
deformation analysis cannot be carried out by considering points directly. This is due to the impossibility of scanning the same point in different measurement epochs, because of the
imperfect repositioning of the instrument and because of the laser beam width [26].
In the present case, the structural monitoring method developed is based on testing whether
deformation occurs between two epochs of structure measurements or not. The use of a
parametric 3D surface generation technique based on RBF function has allowed us to overcome
the single point accuracy of TLS, seeing that surface elements derived from a large number of
points could originate deformation parameters. As a result, a surface analysis is performed
comparing data acquired in different epochs and georeferring them into the same reference
system. Particularly, a deformation analysis using multiple orthogonal cross sections (horizontal
and vertical) is applied to 3D surfaces. With the resulting sections we can extract automatically
3D displacements vectors not only applied to a limited number of points, but also to the whole
wall structure. As a result, a map of deformations which includes the displacements between
different measurement epochs is obtained.