gramm, FMP) which took place in 1976/77 as a government spon- 
sored joint project of several German institutions concerned 
with remote sensing. The experiments in the investigation area 
"Black Forest - Rhine Valley' were directed by G. Hildebrandt 
and included three flight campaigns with a multispectral scanner 
(Bendix M2S) taking place in spring, summer and autumn 1976. 
Each campaign comprised flights, three times a day, in three 
different levels (1000, 2000 and 4000 m above ground level). 
The data recorded in the 8...14 um thermal channel were pro- 
cessed with the digital image processing system DIBIAS in col- 
laboration with G. Kritikos of the DFVLR in Oberpfaffenhofen/ 
Munich. 
  
  
    
   
  
  
  
  
  
  
  
  
    
    
  
  
  
    
  
   
  
  
  
  
  
  
  
  
  
  
  
  
   
  
  
A rough representation of the test area is given in Fig. 1. It 
shows the Black Forest - Rhine Valley boundary and the isolated 
Kaisersthuhl, a mountainous area of about 90 km2. The two 
examples will show the greater part of the city of Freiburg and 
a 16 km“ area situated in the Rhine Valley; these areas are 
shaded in Fig. l. In the vicinity are 4 regular weather stations 
recording wind speed and wind direction. Of these, Feldberg 
(1486 m) is the highest point of the Black Forest and therefore 
is nearest to free atmosphere conditions over Southwest Germany. 
Of the remaining three stations, Bremgarten represents best the 
Rhine Valley. In Freiburg and -less frequent- Bad Krozingen wind 
direction is influenced by valley winds from the Black Forest. 
Example 1 
Fig. 4a is a thermal image of Freiburg taken before sunrise on 
Ist April 1976 from an altitude of 4000 m. Surface temperatures 
(in the following: ST) range from below 0°C to over 10°C. Air 
temperatures were recorded simultaneously and ranged from 6.2 
to. 10, 49C. 
Similar images have been described earlier [RPU 1972, Hirt 1975, 
Stock 1975, Weischet 1975] so that a general description must 
not be given here. The distribution of ST corresponds to what 
one would expect: For example, the wooded hill slopes east of 
the city appear with high ST as radiational cooling can be com- 
pensated for by upper and warmer air. Normal too, is that the 
lowest ST occur over short grass as e.g. on the airfield near 
the northwest corner or that the city centre with its concentra- 
tion of massive buildings has relatively high ST. It should be 
noted, however, that the southern part of the city centre dis- 
plays considerably lower ST compared to the northern part, al- 
though the type and density of the buildings are the same. On 
the other hand, the southwestern suburbs are in large areas