9. The individual distortion values calculated for each 
measured point. 
10. The standard distortion values for each measured point. 
ii. The location of the principal point of auto-collimation 
relative to the centre of symmetry. 
I2. Measurements of fiducial marks. 
I3, Nominal positions of reseau crosses and their errors. 
14. An estimate of the probable errors of the measurements. 
Although some of these items will be covered by definitions in the 
International Standard, it is thought that they should be confirmed cate- 
gorically in the calibration certificate. Moreover the surveyor using 
the calibration certificate may not have a copy of the Standard immediately 
at hand to confirm sign conventions or origin of measurement.  Considerable 
importance is attached to the recording of measured values of angles and 
distances in the focal plane. These enable the surveyor to check the 
distortions quoted or to choose another principal distance if he requires 
it. A mere graph of mean distortion values is quite insufficient when the 
most precise work is being done. 
Some importance is attached to an agreement on the calibration of 
the reseau glass, which is believed to be a major advance in photogrammetry. 
This technique is still in an early stage, so that an agreement on the 
calibration should be possible without upsetting any well established 
practice. 
No attempt has been made in the present paper to draft the two 
sections dealing with the Methods of Test and the Presentation of Results, 
partly for reasons of space and partly because these need to be joint 
effort of workers having experience of the numerous possible methods. It 
is to be hoped that discussions at the forthcoming Stockholm Congress may 
establish sufficient agreement for these sections to be written. 
  
  
  
  
  
  
  
  
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