Full text: Proceedings, XXth congress (Part 5)

   
  
  
  
masking tape is feasible where the surface of pipe is smooth 
and low temperatures exist. It is relatively simple to apply 
masking tape. However, high temperature or surface roughness 
(e.g., rusted surfaces) might be a barrier to employing this 
technique. 
4. 3DMODELLING PROCESS 
Three sets of scanning data were joined using a cloud-based 
registration method, which was introduced recently (Fall, 
2002). Unlike in control/tie point-based registration, the 
registration can be done with points without setting out control 
targets around model space. This application can not only 
eliminate the time and cost for setting artificial targets but also 
reduce the difficulties of setting up targets on or around hardly 
accessible area. Each scan set is registered with minimum of 
three common points. These points can be located anywhere, 
but an edge of an object or very distinctive points should be 
chosen to track them easily in the other scan sets. The resulting 
scanning cloud mosaic captures a part of the table and piping 
objects. 
To model each pipe point-clouds of each object was separated 
by selecting window and "cleaning points" was necessary to 
eliminate unnecessary points, which can be mainly noise and 
points of adjacent object such as a table in this experiment. 
After point-clouds were selected the fitting cylinder was 
constructed. The diameter of cylinders was determined based 
on fitting object. Diameter of each object is compared with 
‘true’ diameter measured by a caliper in 0.01mm. In the case 
of galvanized iron, ceramic, and aluminum the measured values 
from scanning data were within 2 to 4 mm differences, which 
were compared with ‘true’ diameter. However, the difference 
was 17mm with 38mm PVC pipe, and this was unacceptable. 
5. Conclusions 
According to the observation of coverage angles, PVC and 
stainless steel have the smallest coverage angles while brass 
and ceramic pipes have much wider angles. In order to form a 
model properly at least 20 to 25% of coverage angle is 
recommended. 
The effects of dulling spray application were quite 
distinguishable and the results showed 50% to 60% increases in 
coverage angles of point clouds compared to the “as-is” 
condition. Masking tape was tested on the aluminum surface 
and the area of scanning point clouds was increased. As a 
result, the accuracy of the measurement of an object was 
improved. The procedure of applying these media was 
relatively simple and efficient in an industrial environment, and 
their application is reliable for object measurements and 
modeling processes. 
The diameter measurements of piping objects based on 3D 
model fitting showed the measurements were close to the ‘true 
value’ in the case of ceramic, aluminum, and galvanized iron. 
However, measurements on some materials such as PVC and 
Stainless steel were unacceptable range. 
6. References 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
Axelsson, P., 1999. Processing of laser scanner 
data—algorithms and applications. ISPRS Journal of 
Photogrammetry & Remote Sensing, 54, pp. 138- 
147. 
Balzani, M., Pellegrinelli, A., Perfetti, N., Russo, P., 
Uccelli, F., Tralli, S., 2002. CYRAX™ 2500 Laser 
Scanner and G.P.S. Operational Flexivility: From 
Detailed Close Range Surveying, to Urban Scale 
Surveying. ISPRS Commission V, Symposium 2002, 
Corfu, Greece. 
Feng, H-Y, Liu, Y., Xi, F., 2001. Analysis of 
digitizing errors of a laser scanning system. 
Precision Engineering, Journal of the International 
Societies for Precision Engineering and 
Nanotechnology, 25, pp. 185-191. 
Johansson, M., 2002. Explorations into the 
Behaviour of Three Different High-Resolution 
Ground-Based Laser Scanners in the Built 
Environment. ISPRS Commission V, Symposium 
2002, Corfu, Greece. 
Lichti, D.D., Gordon, S.J., Stewart, M.P., 2002. 
Ground-Based Laser Scanners: Operation, Systems 
and Applications. Geomatica, Vol. 56, No. 1, pp. 21- 
33. 
  
  
  
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