the parameters of the method of reconstruction and calibration are the same. 
Then we take photographs of a test object and from geometric information in 
the pictures we estimate the elements of interior orientation using the method of 
least squares. We also estimate the accuracy of the image co-ordinates, and the 
accuracy of the estimates of the elements of interior orientation. This accuracy 
depends on the number of points, their locations in relation to the camera and 
the accuracy of the image co-ordinates i.e. how well the mathematical model 
fits the observations. As the test photographs are taken under conditions 
that are very similar to practice, we may assume that the error population is the 
same for test and practice. This always ought to be applied where measuring 
devices are calibrated. Accurate calibration is absolutely necessary for all 
measuring procedures. This also makes it possible to predict the accuracy in 
future evaluations of pictures from the calibrated camera. The information 
regarding accuracy also provides the possibility of testing certain hypotheses 
with statistical methods. 
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