Trento 1945 
Trento 1973 
  
   
3 Grass and Wooded Area Rural Area & Urban Green 
  
Trento 2009 
  
Rovereto 200 
  
Trento 1945-2009 
1000s 
  
1945 1973 2009 
Rovereto 1945-2005 
    
80a 
60" 
10% 
20% 
      
2005 
® Manufacturing/Commercial Area — m Built-up Area 
Figure 4: Digitization of multi-temporal orthophotos showing dominant landscape changes. The white areas on the GIS layers are 
rivers or roads. In the right column, land cover and land use analyses for Trento and Rovereto cities are summarised. The four 
landscape categories are expressed as percentage of the investigated area (ca 8sqkm for Trento and ca 12sqkm for Rovereto). 
To test the utility of the proposed methodology and resultant 
data layers, specific features were manually digitized as GIS 
layers and then classified into four macro landscape categories 
(adapted from Robinson et al., 2004): 
* built-up or urban areas; 
e manufacturing and commercial areas; 
* rural area and urban green; 
* grass and wooded areas or wild lands. 
The final result was a temporal GIS developed using data 
acquired from the multi-temporal image. This temporal GIS is 
used to identify, document and analyse transformations in land 
cover and land use for the region of interest (Fig. 4). Diagrams 
with relative changes with respect to the entire investigated area 
were also computed. The analyses show that significant urban 
growth has occurred in the post-war years. In particular, they 
indicate that in the southern part of Rovereto, an important 
industrial zone was built and that, generally speaking, while 
urbanization has increased, surprisingly the amount of forested 
land has also increased, most likely due to a decrease in the use 
of firewood. 
5. FURTHER PRODUCTS: 
CITY AND BUILDINGS MODELLING 
The repository of WWII era historical images also comprises a 
set of oblique aerial photos (tilt angles of about 45?). To 
demonstrate the utility of such data and explore the possibility 
to perform further 3D studies and analyses, an oblique image of 
Rovereto was processed following the steps described in section 
3. For this test, the oblique image was incorporated into the 
86 
bundle adjustment with the other vertical images and used to 
manually model old buildings (still existing and not modified). 
The use of Pictometry-like oblique images allowed the 
derivation of a more accurate 3D reconstruction due to the 
higher intersecting angle among homologous optical rays (Fig. 
5a) In order to assess the accuracy of the obtained 
photogrammetric model, a geometric comparison with the 
current LiDAR data was performed (Fig. 5b). The same 
distances were measured on both models—the results indicated 
maximum differences of ca. 50cm. This test demonstrates that 
integrating vertical and oblique aerial imagery is suitable for 
historical 3D city modeling and to reveal changes and 
transformation in buildings. 
6. CONCLUSIONS 
This paper presented a 4D modeling approach that uses multi- 
temporal and historical aerial images to derive spatio-temporal 
information for scenes and landscapes. The case study in the 
Trentino region showed that the digital processing of archival 
images offers a method for researchers to identify changes over 
time in cities and across landscapes. The results indicate that 
processing historical aerial images presents many challenges, in 
particular for actual automated procedures, and the need to 
correctly recover unknown parameters in order to avoid 
substantial geometric errors. In case of image blocks with large 
overlap and a better geometry, a self-calibrating bundle 
adjustment with different sets of additional parameters can be 
employed in order to minimize all the possible errors and 
deformations. A strict photogrammetric processing, like the one