[ERA . CALIBRATION CONSTANT 
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J. À. Eden 
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It is advocated that whatever information is provided on a 
calibration certificate the basic measures of x and © should always be 
included, 
ES STE MSI ST SE EE AA QE NES ES EE ES CES ET EEE SC SES SEE TES 
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& may be expressed by listing 
he measures on the plate to 
The fundamental constants of a came 
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of all camera calibration. Why 
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the external angles of entry 9 against 
which they apply. This is the bas 
is it then that these measures are 
certificate? 
FM 
isted on the calibration 
The usual practice is to state on the calibration certificate a 
value for the principal distance against a Bst of di n eT corres- 
ponding to various angular distances from a int of origin. These 
are not basic measures at all. They are any from the original 
measures by a mathematical process involving various adjustments, 
distributions, interpclations and weightings. It is well known that 
these distortions may be expres sed in a large variety of different 
WAyS. Furthermore, the distortions are often given in the form of a 
graph in which the Punber of obse E d ions made and the degree of inter- 
polation employed is effectively hidden. 
The writer believes that the analysis of | the basic measures should 
be undertaken by the photogrammetrist using a method which suits best 
his own purposes, and that there is no need for the analysis of these 
measures to be undertaken by the calibrating er erem If this 
principle was adopted it would altogether absolve the calibrating 
authc rity from the necessity of explaining his computing techniques. 
Under present practice if he does not do this in sufficient detail it 
is impossible for the photogrammetrist to work back from the data 
supplied to determine correctly the original observations. The 
is essential for him to know if he wishes to determine his own 
distortions by a method most suitable for the task he has in mind. 
  
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The writer therefore advocates that whatever information is 
provided on a calibration certificate, the basic measures of x and 
A 
should always be included. 
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