ibul 2004 
ates will 
s on the 
levation 
nage 
oimage 
lan view 
must be 
D model 
material 
  
nage 
  
  
ion 
The developed algorithm uses a set of data in order to produce a 
true orthoimage: 
Interior Orientation 
Exterior Orientation 
3D Model 
Us N — 
In Figure 4, the build up algorithm for true orthoimage is 
illustrated. 
The input data refer to the structure of the 3D model, the 
interior and exterior orientation. According to the needs of the 
orthoimage the output pixel size is defined. The extents of the 
orthoimage are determined by the boundaries of the 3D model. 
Every pixel in the true orthoimage is calculated according to its 
position inside a specific close region of the 3D model. The 
texture for pixel values is taken backwards from the original 
images through the exterior orientation and the collinearity 
equations. 
4. TESTING THE ALGORITHM 
  
  
(b) 
Figure 5. (a) The conventional orthoimage. (b) The true 
orthoimage. 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
The developed algorithm is applied under real conditions, in an 
architectural Photogrammetry case study. The building shown 
in Figure 5 is under renovation and the photogrammetric 
restitution of all the facades is needed. 
In Figures 5 (a) and (b) the products of conventional 
orthoimage and the true orthoimage respectively are illustrated. 
The differences are mainly visible in areas where the building 
lean problem is obvious.