the structure coordinate system, whereby the 
X - axis is identical with its longitudinal axis 
(Bregor, 1991). 
The Basic geometric parameters of the checked 
cable bridges are given in Table 1. 
- transformation of detail points coordinates into 
  
  
  
  
  
  
  
Main parameters of bridges Table 1 
uspended Bridge Distance of |Max.cable|Pylone 
cable bridge| length | anchoring sag height 
blacks 
m 
Piestany 76.23 116.2 7.0 12.25 
Nelahozeves 160.83 233.5 14.80 22.85 
Winter port 145.95 225.9 13.4 25.85 
  
  
  
  
  
  
  
2.1 SURVEYING MEASUREMENT 
The surveying micronet in the shape of a quadran- 
gle was created by four camera standpoints, that 
means terminal points of photogrammetric base 
lines flanking on both sides of the bridge. The 
quadrangle was measured by angles as well as 
lengths using the EDT 208080 Zeiss Jena distance- 
meter. By using the forced centering we secured 
the accuracy of point determination with a mean 
coordinate error ny = 8.004 m. 
The surveying micronet points define partiy the 
spatial position of projection centers for the 
y : P2 
    
      
    
    
   
     
  
     
    
     
     
     
    
     
  
    
     
   
    
      
    
    
    
      
      
   
     
     
  
   
analytical spatial intersection and at the same ti- 
me they are the standpoints far determining control 
points that are used to adjust coordinates of the 
structures detail points determined by means of 
the photogrammetric method. 
2.2 TARGETINS 
Ta target the control points we utilized partly 
surveying targets on a tripod (Freiberg circular 
target) with the possibility to turn them perpen- 
dicularly to the direction of the camera axis, and 
partly ball targets (Fig.l) independent from the 
direction of the camera axis. At inaccessible 
places we used points of the structure, that can 
be unambiguously identified, as natural targets. 
Together with the orientation point the optimum 
number gives § control points for one pair of 
photographs. 
+a 
«3 PHOTOGRAPHY 
During the measurements of the given bridges the 
wide-angle universal camera UMK 108A Zeiss Jena 
proved to be the optimum camera type, whereby it 
was in all cases possible tn take phatagraphs with 
a horizontal camera axis. The photogrammetry 
accuracy is a function of the photograph scale, 
and therefore we try to choose the photogrammetric 
base lines as near to the measured structure as 
possible. However, the decisive factor is the re- 
quired accuracy, in the given case less than 30mm. 
  
Fig.2 The numbering 
   
system of the structures detail 
   
points.