-57 
The mesh used for the data noise reduction is of 0.24 gon, 
which means an average distances between the filtered points of 
about 15 cm. 
The filtered scans were registered using the reference system of 
acquisition 1 as the local reference system for the 3D model. 
Figure 19 shows two adjacent scans in their own reference 
systems while figure 20 shows the two scans oriented in the 
reference system of the final 3D model. 
Finally, the 3D model was converted into DXF and VRML 
format (see fig. 21). 
Figure 18. Original and filtered scan 
The 3D model is now ready the subsequent elaborations (e.g. 
true orthophoto production, geometric interpretation,...). 
The whole procedure has been performed, using a standard PC, 
in less than 40 minutes. 
Figure 19. Adjacent scans in the acquisition reference systems 
Figure 20. Adjacent scans in the 3D model reference system 
6. CONCLUSIONS 
Laser scanner device producers offer many different types of 
software for the geometric management of the acquired data. 
These software packages were developed for mechanical 
application purposes but they are not able to supply an adequate 
answer to the particular field of architectural surveying. 
While mechanical applications usually have to describe 
standard surfaces (e.g. spherical, cylindrical), architectural 
surveying has to manage complex surfaces that cannot be 
simplified. 
The proposed algorithm and its practical application through the 
LSR package offers the possibility of correctly managing the 
data acquired using terrestrial laser scanner devices for the 
surveying of architectural objects. 
Figure 21. 3D model managed by COSMOS VRML viewer 
The software automatically runs some basic procedures but 
requires direct intervention for some special procedures, 
allowing maximum flexibility. 
The automation level reached by the LSR software allows even 
unskilled operators to use the acquired data; all the problems 
that involve specific metric survey knowledge are solved by the 
software itself. 
The 3D model produced by the LSR is not the final product of 
the survey but represents the correct starting point for vector 
extraction, 3D image model construction and basic geometric 
interpretation. 
7. REFERENCES 
Boccardo P., Comoglio G. (2000). New methodologies for 
architectural photogrammetric survey. International 
Archives of Photogrammetry and Remote Sensing, Vol. 
XXXIII, Part B5/1 
Roggero M. (2001). Dense DTM from Laser Scanner Data. 
OEEPE Workshop “Airborne laser scanning and 
interferometric SAR for detailed digital elevation models” - 
Stockholm 
Beinat A., Crosilla F., Visintini D. (2000). Examples of 
georeferenced data transformations in GIS and Digital 
Photogrammetry by Procrustes analysis techniques. 
ISPRS joint meeting “Bridging the gap”, Ljubljana 2-5 feb. 
2000 
8. ACKNOWLEDGEMENTS 
The research has been financed by Italian Ministry of 
Education, University and Research (MIUR) project 
COFIN2000 (Nat. Resp. Prof. Carlo MONTI - Research Group 
Resp. Prof. Sergio DEQUAL).