APPLICATION OF TLS FOR CHANGE DETECTION IN ROCK FACES

The paper describes some experiences carried out in monitoring of two rock faces in Italian Prealps in order to detect changes due to rock detachments. Since the forecasting of possible rockfall events is the main aim of this research, terrestrial laser scanning application was investigated for high precision def ormation monitoring in this context. Firstly, probl ems concerning the data acquisition and the reduction of georeferencing err ors are analyzed by comparing results obtained from different approaches. A method including the use of a removable steel pilla r to constrain the 3D shifts of the instrumental re ference system, and of ICP surface matching algorithm to solve for rotations g ave the best results. Secondly, some techniques for filtering vegetation from pointclouds of cliffs are presented and discussed here. These are mainly based on 3D spatial filters. The u se of an infrared camera integrated to terrestrial laser scanner is also pro posed. Finally, results on the comparison of multi- temporal laser scans are presented, showing somehow the proposed pipeline can be successfully applied to detect small rock detachments of the size of a few cube centimetres. 1. INTRODUTION

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