AREAS 
ly 
lerive spatio-temporal 
loto interpretation and 
ie fourth dimension of 
describe, and analyse 
ch are historical aerial 
tabase. The proposed 
itino region in North- 
'S such as topographic 
understand landscape 
  
| data and identify 
as across landscapes. 
st researchers as they 
ngs and understand 
'esearchers have used 
purposes like: (1) 
atcliffe & Henebry, 
f change detection in 
, (3) creation of 4D 
>s (El-Hakim et al., 
anges (Stefani et al., 
2010) and (6) urban 
elling approach using 
tudy. The employed 
cal and more recent 
order to acquire data 
iformation. Rigorous 
iques for image 
SM) production and 
torical photos dating 
order to derive metric 
t scenes. From these 
data, the layers of a temporal Geographic Information System 
(GIS) are created. These GIS data are then used to compare 
historical scenes (e.g., WWII) to scenes from more recent 
imagery to document and investigate changes through time in 
landscapes, vegetation and anthropomorphic features such as 
buildings, roads, etc. 
  
Figure 2: Typical strip of historic aerial reconnaissance photos 
for Trento depicting a non-constant overlap of the images. 
2. THE AVAILABLE DATA SETS 
The aim of the project is to create a multi-temporal spatial 
database for the cities of Trento and Rovereto and their 
neighbouring areas in the province of Trentino. These two areas 
were selected as case studies because significant infrastructure 
and landscape changes were expected. 
Heterogeneous datasets representing different time periods were 
collected and used: 
e Black and white historical aerial images (physical prints) for 
Trento (Fig. 2) and Rovereto acquired during 
reconnaissance flights dating back to the Second World War 
(WWII). These analogue photos were not supplied with 
camera calibration certificate - mandatory information for 
photogrammetric processing; 
* | meter resolution black and white digital orthoimages for 
Trento and Rovereto derived from a photogrammetric flight 
in 1973; 
83 
e 0.5 meter resolution RGB digital orthoimages for Rovereto 
produced from a photogrammetric flight in 2005; 
e 0.5 meter resolution RGB digital orthoimages for Trento 
produced from a photogrammetric flight in 2009; 
e | meter DSM and Digital Terrain Model (DTM) from aerial 
LiDAR data collected in 2006. 
The WWII photos needed to be processed and geo-referenced in 
order to produce orthoimages comparable with the other 
available datasets. A set of eight vertical images for Trento and 
five for Rovereto were selected for processing (Table 1). To 
achieve a complete stereo coverage for Trento (from the 
northern to the southern part of the city) two different sets of 
acrial photos were selected. 
  
  
  
  
  
  
  
  
  
  
  
  
  
Trento Rovereto 
Numb. used photos 6 2 5 
Possible camera K-17 K-17 K-17 
Image format 9x9 in 9x9 in 9x9 in 
Date of flight 24/4/1945 | 29/4/1945 | 29/4/1945 
Possible focal length | 609.6 mm | 609.6 mm | 609.6 mm 
Approx. scale 1:13 000 1:12 500 1:12 500 
Approx. GSD 0.2m 0.2m 0.2m 
Image overlap ca 60% ca 60% ca 60% 
  
  
Table 1: Historical images (1945) used in the project. 
2.1 The WWII reconnaissance imagery 
The oldest sets of historical aerial images belong to a repository 
of photographs acquired during WWII by the Royal Air Force 
(RAF) and United States Air Force (USAF) airplanes. 
Following air raids, reconnaissance flights were conducted to 
ascertain impacts of bombing missions. 
During WWII, fighter planes such as the British Spitfire, the 
Mosquito, the American P-38 Lightning and P-51 Mustang 
were adapted for photo reconnaissance. These airplanes were 
stripped of weapons and painted in sky camouflage colours for 
making it difficult for them to be recognised by the anti-aircraft 
artillery. Additionally, the planes’ original engines were 
modified to ensure good performance at very high altitudes, 
which also helped prevent them from being intercepted. To fly 
at such high altitudes required the employment of very long 
focal length and the development of a camera warming system. 
Various types of medium and large-format cameras were used 
and arranged in different configurations (both vertical and 
oblique) to ensure wide ground coverage (Leoni & Marchesoni, 
1997). Most of the aerial cameras had vacuum backs with a 
retractable pressure plate and a vacuum piston that kept the film 
flat and fixed in the focal plane during exposures. 
Massive air raids were conducted over Trento and Rovereto 
between 1943-1945 to destroy landline communication and 
sources of energy that supported Nazi and Fascist armies (Leoni 
& Marchesoni, 1997). During this time, typically before and 
after the bombing missions, more than 1000 vertical and 
oblique photos were taken. These WWII images are available as 
contact prints from the original historical films provided by the 
American NARA (National Archives and Records 
Administration) and London and Keele University archives. 
The prints from both vertical and oblique images were supplied 
with neither camera certificate nor flight information. This lack 
of information about the camera, lens, etc. along with the 
photographic product (i.e., contact print from historical films) 
posed several challenges following a rigorous photogrammetric 
workflow.