N N te eh GP AR Rs SINR orange pg utc ipo t ai a peque tme ament M e Og aa dicitur N El CA oath 
2.5 | Changes in Calibrated Focal Length 
Regarding the accuracy of photogrammetric plotting processes, the 
calibrated focal length is not as important as the distortion. 
Therefore, it is only ascertained with an accuracy of t 0,02 mm 
during calibration. Nevertheless the influence of air pressure 
and temperature on the calibrated focal length is of interest. 
It results from the alteration of the focal length and the 
distortion of radial distance 140 mm. The total influence is 
listed below: 
  
  
  
  
  
  
  
  
  
  
  
Changes in Calibrated 
installed Exposed to atmosphere 
in pres- 
surized cabin 
(with cover (without cover glass) 
glass) 
lens temp. lens temp. 
constant +7 dep.on ext.temp. 
flight height 6 km | 1^ km 6 km 14 km| 6 km 14 km 
S-Pleogon A4/85 -0,005 | -0,019 | -0,025 | -0,038 |-0,045 |-0,076 
Pleogon A 4/153 -0,020 | -0,038 | -0,036 | -0,058 |-0,047 |-0,080 
Toparon A,5,6/210 | +0,014 | -0,007 | -0,021 | -0,013 -0,082 |-0,127 
Topar A 5,6/305 40,012 | -0,01? | -0,025 -0,028 |-0,110 |-0,172 
- table 4 
Focal Length (in mm)- 
You will note that these changes may reach the accuracy and should 
therefore be taken into consideration. Also, it is obvious that 
the alterations are by no means proportional to the focal length, 
but depend upon the type of lens.