[. 
Fig. 
rear seats. In that case the right front seat must be reserved for the 
photographer and a distant handled mounting is suitable. 
The inner orientation was settled and the camera was carefully tested 
and adjusted at the Royal Institute of Technology. 
The radial distortion was determined by the horizon method from 
photographs from the time before and after the expedition. Using the 
parallax-method!) distortion-curves were even produced from pictures 
taken in Ecuador. l'or results see figure 3. 
The camera was also checked with regard to resolving power and 
reliability and efficiency of the shutter. 
The measurements and calculations mentioned above were carried 
out by civil engineer Einar Rehnlund. 
Five different types of filters were tested by the Division of Pho- 
tography. Three of them were rejected because of a strong fluorescense. 
Two Kodak Wratten filters Nos. 9 and 15 showed good qualities and 
were used during the expedition. In the moist tropical air the deep 
yellow filter gave the best results. 
A Wild C 2 camera (plates) was on board as stand by. 
1) Hallert, B.: Determination of the Radial Distortion of Aerial Cameras in the 
Air from y-Parallax-Measurements. Manuscript. 
  
    
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