Figure 7 install field and point cloud of installed colomns 
4.1.1 Registration of point cloud 
Planar targets of HDS4500 are used in the registration and 
coordination transformation of point cloud. Figure 8 shows the 
control network of national stadium, targets used for 
transformation are stitched with reflectance patches and temp 
targets are set for registration of scan stations. The accuracy of 
registration is +3mm and transformation accuracy is t5mm, 
which could meets the pricision requirements. 
  
Figure8 Control network of National Stadium 
4.1.2 Extraction and comparison of feature points 
Box-vertex points are being compared mainly and thickness is 
considered either. Connors feature are extracted mainly through 
intersection of planer patches and the fitting error of plane 
is 2mm . After extracting of feature points, the ports on 
ground is compared with the size left between columns and 
corrected according to the result. 
4.2 Slippage and installation quality monitoring of 
national gymnasium roof construction 
National gymnasium is one of three Main Venues of 29th 
Beijing Olympics Game. Total construction area is 80890 
square meters reinforced concrete structure. The installation of 
the roof steel structure is done through installing the hinge and 
forward sliding of the ways. In the procedure of installation and 
sliding, high precision surveying and inspecting of the steel 
structure roof truss is necessary to keep the quality assurance of 
construction. National gymnasium roof consists of 14 trusses to 
support the buildings framework. The roof rack hinged by 
increasing and slipping from east to west, there are mainly three 
slides (see from Figure 9). 
4.2.1 Combination of Targets and control points 
The process of steel installation is generally sliding a welded 
frame and then next frame is left continually, at last the entire 
  
© Scan station 
® control points 
Figure 9 Scanning sites and distribution of control points 
frame is installed. So general observation period is selected at 
the time after a hinged sliding distance, and then another 
observation is made after next welded frame is finished. Two 
parts of the data are connected as a complete observation period. 
  
Figure 10 point cloud of five frames 
HDS3000 (Leica) is selected in actual observation, the furthest 
scanning distance of the scanner could reach 200-300m, with 
point accuracy 3-5mm in working zone, the scanning view is 
360x270 degrees; Scanning point interval is 10mm. 
According to demands of observation object, four relatively 
fixed observation sites is designed. Figure 10 shows the 
observation point cloud data when five frames are sided. 
4.2.2 Feature Points Extraction 
Scanning targets is used in point cloud registration, which are 
acquried in the scanning progress and with the the precision 50 
meters /+1.5mm . These points can be used either for 
registration of different scanstations or for transformation of 
coordinate system. All periods of point cloud could be 
transformed through the control points. The part of surveying is 
divided manually according to the target. The feature extracted 
includes spherial-shaped and rod-shaped. The fitting error is 
«2mm . Some node adopts the rods intersection access to the 
actual feature nodes. 
4.2.3 Comparison with total station 
  
     
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