remove re- 
In average 
itched. The 
3D gridded 
jacing. The 
verall accu- 
in the over- 
4 was done 
with topog- 
nts were in- 
ed. The dif- 
ition of the 
Max abs. 
error 
0.12 
  
  
0.18 
0.09 
0.15 
0.18 
ige pairs 
nages). 
  
ones with 
n with the 
1g (Fig. 8). 
nds on the 
as signifi- 
mall errors 
:lected and 
andard de- 
  
al of 0.01 
  
  
  
       
uu 
Figure 9. Shaded relief of same are as in figure 8 
The matching performed on the 2 virtual images, generated 
from the images of the 2 strips gave an average accuracy of 
0.06 m. The DSM was filtered and gridded to 0.02 m grid. 
The accuracy suffices for archaeological documentation; 
therefore virtual images can substitute sequences of images. 
5.6 Conclusions 
Virtual images can substitute sequences of images if the accu- 
racy degraded by assuming that the object space is a plane, is 
sufficient for archaeological documentation. In case of higher 
accuracy, a DSM should be used in the algorithm. Therefore 
there are two possible ways to work with virtual images. Ap- 
proximating the terrain with a plane and generating virtual im- 
ages that can be used for the extraction of the 3D surface or us- 
ing the normal images, extracting the 3D surface and generating 
the virtual image using this surface. Then, the virtual images 
can be stored and used for further processing in the future. The 
extraction of the 3D surface depends on the accuracy of the es- 
timation of exterior and interior orientation. The use of virtual 
images leads to image data size reduction and easier handling. 
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