92 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1976 
INTERIOR AND EXTERIOR ORIENTATION 
REMARKS REGARDING THE CAMERA GEOMETRY 
If metric data are to be derived from a photograph, sufficient additional information is 
required to reconstruct the object bundle which formed the photograph. 
Letus assume for a momenta distortion-free lens. In this case the photograph can be put into 
the object bundle, in position i, in such a way that the projection center O, the image point p, 
and the actual point P are located on a straight line. This condition—the collinearity 
condition—holds true for all points photographed with this lens (see Figure 1). 
In order to reconstruct the object bundle from the photograph it is necessary to define the 
projection center 0 with reference to the image. 
First, it is stipulated that the projection center is located on that object ray which is 
perpendicular to the image plane. This ray will be referred to as the chief ray, and its 
intersection with the image plane as the principal point of autocollimation. In practice, the 
  
ABSTRACT: This paper discusses the use of non-metric cameras in 
photogrammetric applications. The derivation of the elements of in- 
terior orientation, using control points in the photographs, is formu- 
lated providing the possibility for "self-calibration" of non-metric 
cameras. Various projects concerned with monitoring high speed 
processes using non-metric cameras, which were carried out at the 
National Research Council of Canada, are described. The accuracy of 
the obtained information is evaluated. 
RrsuMÉ: Cet exposé étudie l'usage des chambres non-métriques en 
photogrammétrie. La dérivation des éléments d'orientation in- 
térieure se servant de points de contróle dans les prises de vues est 
formulée donnant la possibilité d’ “auto-calibrer” les chambres 
non-métriques. 
Plusieurs projets, éxécutés au Conseil National de Recherches, 
touchant au contrôle de procédés à grande vitesse et utilisant des 
chambres non-métriques sont décrits. La précision des résultats est 
évaluée. 
ZUSAMMENFASSUNG: Die Verwendung nicht-metrischer Kameras für 
photogrammetrische Zwecke ist Gegenstand dieses Berichtes. Die 
Herleitung der Elemente der inneren und der äußeren Orientierung 
mithilfe von im Bild gegebenen Kontrollpunkten wird besprochen. 
Verschiedene, am National Research Council of Canada durch- 
geführte Auswertungen von Aufnahmen sich schnell bewegender 
Objekte werden erläutert und Hinweise auf die erzielte Genauigkeit 
gegeben. 
  
image plane i is located on the image side of the projection center parallel to the plane i; the 
principal point of autocollimation is then defined as the point of intersection of the chief ray 
and the image plane i. This ray is, prior to entering the lens, perpendicular to the image plane 
i. After passing through a lens, which introduces a certain amount of distortion, the chief ray 
will, in all likelihood, no longer be perpendicular to the image plane i. The advantage of the 
above definition for the principal point is that it can be determined by autocollimation. In 
practice, however, the point of best symmetry is used to define the projection center with 
respect to the image plane. For the point of best symmetry, the radial lens distortion is, to the 
best approximation, rotationally symmetrical, giving certain advantages in the correction 
procedures. 
In addition to the principal point, the distance between projection center and the image 
plane is needed. Most amateur cameras will have the same image scale in all directions. Some 
professional movie camera lenses, on the other hand, have a non-uniform image scale to 
accommodate screen format requirements. These lenses are called anamorphic lenses. The