Pitout, Cedric 
  
  
Shadow Supposed coal tar 
    
Coal tar 
Figure 4. Coal tar zones location 
  
  
  
In our first case-study for example, coal tar has a characteristic surface "signature" relatively easily to determine on an 
aerial photograph and to digitize (Figure 4). Nevertheless, it is important to take into account limits of the photo- 
interpretation, in particular with the risk of confusion between shadows and waste coal tar. The repetition of this job on 
all aerial views show that the actual contaminated zone limit is quite good located. Yet, the figure 5 questions site 
activity archives since they mention only two quite good limited tar lagoons. With aerial views study, it seems that a 
large part of this zone has been recovered by coal tar during site activity. 
  
The case-studies show that we do not 
have a site in activity and then a 
completely open brown field. First of 
all, there is a transition period with the 
end of production, demolition,... and 
sometimes decontamination and 
remediation. Aerial photograph and 
visits on sites indicate that brown fields 
zones are used for storage of several 
kinds of autochthon or allochthon 
materials (clay, contaminated soils, 
vegetation, etc...). For instance, the 
former coke plant, the area called 
"contaminated zone" (cf. Z.C. on the 
figure 3) has been recovered and then 
smoothed on it quasi-totality with zinc 
dust. 
  
  
  
  
Figure 5. Coal tar deposits during site activity 
  
  
4.4 Aerial photograph contribution 
  
The use of aerial photographs provides some information which is difficult and even impossible to get by any other 
way. From the oldest views, we can follow the global site evolution. Moreover, we can control the management of 
removing and packing, or to locate the most polluted areas. Limitations of use are due to the photograph availability and 
quality and related interpretation difficulties. For instance, periods of site activity start often before the first aerial 
surveys. 
Moreover, if the survey frequencies are irregular and/or the site have known rapid transformations, some information 
can be lost. Nevertheless, relatively to the poverty of other archives, these limitations are not so problematic. 
S CONCLUSION 
The structure and data organisation has to be logic taking into account all of these aspects of a site description and 
analysis, but forecasted with an “open strategy" allowing to append some new fields. A specific attention has to be paid 
  
1160 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.