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Figure 10. Detail of the photorealistic rendered 3-D model. 
6. CONCLUSIONS 
The described experiment permitted the analysis of 3-D models, and the evaluation of their characteristics, in relation to 
time and cost. As a result, it can be said that 3-D photorealistic models can be very useful to represent urban areas, 
through both perspective views and animations, in particular because 3-D models can be very detailed and easy to use at 
the same time. Nevertheless, long processing time is needed to create such models and this can affect costs. From a 
more technical point of view, the textures displayed on the screen are of poor quality; this is because the rendering 
software is mainly conceived to produce pictures taken from different points of view and animations. So, it can be more 
appropriately used to create printed images or films, integrating CAD representations of buildings and the urban 
environment with information about building surfaces, materials and their state. 
If other application are implemented, i.e. the simulation of physical phenomena within in some urban space, and 
particularly the propagation of electro-magnetic waves, the time and expense necessary to produce a photorealistic 3-D 
model are to high. In these cases, it would be probably better to use monochromatic 3-D models. 
Indeed, notwithstanding this kind of model is made up of simple surfaces, it is useful to study the intervisibility of 
points, and the presence of obstacles to lightwaves, radio waves etc. It can be useful, for example, for planning of 
mobile-telephony antennas, and simulating the signal propagation from broadcasting antennas to receiving ones. 
Radiation used in mobile telephony communications is radio frequency (RF) one. The propagation of radio waves 
depends on the intensity of the signals, and on the absence of obstacles in the way of the signals. Therefore, it is 
important to know well the morphology of the territory and the layout of the objects and building volumes on it. 
By modelling the electro-magnetic radiation given out by a source, and fixing the position, signal intensity and 
frequency of their source, it is possible to show the direction of rays, and control their transmission range and field. 
Moreover, by assigning different colours to the various represented areas, in relation to signal intensity, one can asses 
the best antenna positions, and control possible shadow areas, that is where the signal is interrupted. 
As a result of these considerations, the monochromatic conventional model was chosen as a suitable support for 
monitoring and testing the behaviour of radio waves employed for mobile telephony communication in urban areas. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 925