ildings have been re- 
stereoscopic photo- 
ages. Each building 
level, in order to re- 
ch can be eventually 
  
nos image) 
  
lly documented by 
he use of amateur 
in average scale of 
, in order to reduce 
ows. A total of 250 
Using the above mentioned control point frame (ie. 2 points at 
the ground level and 2 points at the roof level, all at the facade 
corners), the facade images have been rectified, mosaicked, and 
draped on the 3D building model for a full-view facade at a 
scale of 1: 50, and at a ground pixel size of 2 cm. 
Finally, for each building, a thorough research at official and 
individually-owned archives, as well as a literature survey re- 
vealed a wealth of historic information, concerning engineering 
drawings (floor plans, facade construction details, etc.), old 
photographs, ownership records, protection status and plans, 
etc. All this information has been collected, transformed to digi- 
tal form and "intelligently" archived in form of Databases with 
proper links to old and new images, document files and further 
bibliography. 
Furthermore, the Information System has been designed and 
developed for access through the Web, with the use of HTML 
pages, as is explained in section 5. 
  
(b) The protected buildings are viewed as 3D rendered 
blocks on top of the draped orthoimage, during flyover 
  
(c) Choice of virtual video walk-throughs 
Figure 3. 3D modelling and Visualization of the city center. 
4. 3D MODELLING AND VISUALIZATION 
OF THE HISTORICAL URBAN CENTER 
The developed mapping material aims at the familiarization and 
orientation of the user through space in different scales and 
resolution. It also aims at giving a visual impression of the 
whole urban area and of the historic center in particular. And 
(d) When "on-ground", the user can also view closer the 
facades of the protected buildings 
achieves all that without sacrificing the geometric quality. In- 
teresting and related to our approach, techniques have been re- 
ported (Bartolota et. al., 2000, Boulanger et. al., 2000, Chikatsu 
et. al., 1998, Gemenetzis et. al., 2001, Ogleby 2001). Also 
worth noting are currently developed low-cost video techniques 
for recording architectural structures (Sechidis et. al., 2001, 
-397-