Alternative method of analysis of results of 3D terrestrial laser scanning (comment to the article “Contribution to a rock block slide examination by a model of mutual transformation of point clouds”, Acta Carsologica 38,1)

Abstract

The article Konic et al. (2009) describes efforts to find out if the rock block on which the castle of Črni kal is situated slid away from the Kraški rob wall. 3D terrestrial laser scanning has been used to determine positions of many points on both presumed contact surfaces and 12-parameter affine transformation that transforms the cloud of points from one wall into another has been found. The deviation between matching point clouds has been used as a test of the original hypothesis. It has been concluded that the rock block did slide. Some of the data from the article are re-analysed using another numerical method. A 6-parameter translation composed with rotation that best transforms the 12 published points from the rock block wall into their counterparts on the Kraški rob wall is found. The original hypothesis is confirmed and some additional insight into the block slide is revealed.

Keywords: rock block slide, 12-parameter affine transformation, rotation matrix, translation vector.