The color film (Ektachrome MS Aerographic 2448 diapositive film) was 
underexposed 2-3 stops, followed by special processing (Hansaluftbild 
procedure). As claimed by Winkelmann (1977), this procedure is appropriate 
for bad weather and winter, and gives better results in practice than 
Le comparable black-and-white film. Interpretation was done monoscopically 
r by a first-time interpreter on the film originals (diapositives) with a 
magnifying glass, using an overhead projector as a light-table. Only in 
this way would sufficient light be transmitted by the diapositives to 
ame). permit an easy and reliable identification of cars. This set-up produced 
& X-mas tree effect: all cars showed up brilliantly against the relatively 
dull background of streets, roofs and green areas. 
te From the black-and-white negative film, normal positive prints were made. 
The plotting was done on maps, scale 1:2500, which took 15 hours from the 
= black-and-white prints, and 11 hours from the color diapositives. Both 
interpretations were highly reliable and provided a complete coverage of 
all cars parked in the open air in the 2 km2 area. 
he 
The more than 25% saving in interpretation time by using color material 
3 was not surprising, as color really makes car identification much easier. 
  
pam ip 
  
Photo 2: Part (1%) of 23 cm format vertical photograph, 
enlarged 5x, scale 1:1000