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2. Introduction 
j 
Most procedures in photogrammetry are based upon the assumption that the 
images are central projections of the objects. In many procedures the bundles 
of rays of the central projections are reconstructed. The central projection is 
also the basis for the projective relation between object and image. Calibration 
of pictures, cameras and projectors is a determination of some properties of the 
corresponding central projection. In this thesis the calibrations concern only 
the geometric properties of the images. Image quality described in terms of re 
solution or contrast transfer is not treated. The geometric properties of the cent 
ral projection, that are necessary to make it possible to reconstruct the bundle 
of rays, are given by the elements of interior orientation. Calibration of came 
ras, projectors and pictures is thus of basic importance for almost every photo- 
grammetric procedure. 
The methods to determine interior orientation can be divided into two groups, 
namely, a laboratory group and a field group. In the laboratory the determina 
tion can be done under well controlled and ideal conditions, while the field 
methods can give the data under operational conditions. The International So 
ciety for Photogrammetry, ISP [5], recommends laboratory procedures for cali 
brating cameras. These recommendations are suited to aerial cameras and colli 
mator techniques. Thus they apply to cameras focussed on infinity. 
Using field methods for calibrating cameras provides some advantages. 
1. They can be used for close-up cameras focussed on finite distances. 
2. They provide the interior orientation and the accuracy of the image co 
ordinates under operational conditions. 
3. They can check a laboratory calibration under operational conditions. 
4. They usually do not require so expensive instrumentation as laboratory 
methods, but instead, demand test fields. 
The calibrating methods described in this thesis aim at a determination of 
the elements of interior orientation, their accuracy and the accuracy of the ima 
ge co-ordinates in one and the same procedure. This is done by photographing 
three-dimensional test objects, measuring the image co-ordinates and compu 
ting the desired quantities on the basis of the method of least squares. In order to 
get a representative sample of the image co-ordinates and to increase the num 
ber of degrees of freedom, the points should be uniformly distributed over the 
image area and so many that it is possible to test hypotheses on the elements 
of interior orientation and on the distribution of the residual errors.