591 
TLS DEFORMATION MEASUREMENT USING LS3D SURFACE AND CURVE 
MATCHING 
O. Monserrat, M. Crosetto, B. Pucci 
Institute of Geomatics, Castelldefels, Barcelona, Spain, - (oriol.monserrat, michele.crosetto, barbara.pucci)@ideg.es 
KEY WORDS: Terrestrial Laser Scanner, Point Cloud Matching, Deformation measurement, Precision, Curve Matching 
ABSTRACT: 
During last few years the use of Terrestrial Laser Scanner has increased notably in different application fields, like architecture, 
geology and geodesy. The paper focuses in the use of TLS data for deformation measurement and monitoring purposes which 
concerns both engineering geology and geodesy. The paper presents a new approach for deformation measurement which fully takes 
advantage of the TLS data characteristics. The procedure is based on the point cloud matching algorithm Least Square 3D Surface 
Matching proposed by Gruen and Akca (ISPRS Journal, 2005, 59, 151-174). The proposed approach takes advantage of both surface 
and curve matching to improve the co-registration quality and it exploits the high density of TLS point clouds, which counter 
balances the relatively poor precision of the single TLS points. The work describes the proposed deformation measurement 
procedure, and discusses in particular some results of the research made at the Institute of Geomatics: the preliminary results 
obtained with curve matching. 
1. INTRODUCTION 
In the last years, the Terrestrial Laser Scanner (TLS) has been 
an increasing interest as a method for deformation measuring in 
different fields such as engineering geodesy (Alba et al., 2006 
and Schneider, 2006) and several applications of geology and 
geotechnics like landslide monitoring (Bitelli et al., 2004) and 
rock falls (Alba et al., 2005). At the same time the availability 
of different typologies of TLS instruments has increased. A 
classification of available TLS can be found in Frohlich and 
Mettenleiter (2004). This increasing interest is due to the key 
advantages of the TLS with respect to classical techniques, e.g., 
the high sampling density, the portability and the automatic 3D 
point measurement. The first one is a key point to counter 
balance the relatively poor quality of the single TLS points and, 
as a consequence, to measure deformations. 
The paper presents a new methodology for land deformation 
measurement from TLS data. This procedure takes advantage of 
the high redundancy of the point clouds for estimating the 
deformation parameters. The core of the procedure is the point 
cloud co-registration based on the least squares 3D surface and 
curve matching proposed by Gruen and Akca in 2005. 
The work is organized in three main parts. Firstly is described 
the proposed deformation measurement procedure which 
includes three main steps, the acquisition of the data, the global 
processing of the entire scene and the estimation of the local 
deformation. In the second part the first results obtained with 
the proposed procedure are presented, and finally the 
preliminary results obtained with curve matching are discussed. 
Some conclusions follow. 
2. PROPOSED APPROACH 
The proposed approach takes full advantage of the geometric 
information contained in the point clouds acquired during 
different epochs, in order to maximise the sensitivity to terrain 
changes. The core of the procedure is the least squares 3D 
surface matching described in Akca and Gruen (2005) and 
Gruen and Akca (2005), which has been implemented by the 
Institute of Geomatics. The procedure is flexible and can be 
used in a wide range of applications. Figure 1 shows the data 
flow of the whole procedure, whose main steps are described 
below. 
TLS acquisitions 
♦ | Remove movement areas 
Figure 1: Data flow of the proposed procedure. Its key points 
are highlighted in bold. 
1. Acquisitions of the TLS data: Let’s assume to have a 
deformation area to be monitored, which is surrounded by a 
stable area. The data acquisition involves at least two steps: