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In close-range photogrammetry both metric and non-metric cameras are used. The 
distinction between the two types is made on the basis of their interior orientation. While metric 
cameras are designed as survey cameras and possess a well-defined interior orientation, non- 
metric cameras, in general, do not incorporate fiducial marks, and their mechanical stability is 
rather questionable, The main attractive feature of non- metric cameras is their flexibility as far 
as focussing distances are concerned. While the several available close-range photogrammetric 
cameras (single cameras, stereometric cameras, and phototheodolites) are extremely well 
suited for many applications, their range of focus is rather limited; and this excludes their use 
in many applications. Furthermore, applications involving photography from unstable platforms ‘ 
and those requiring quick succession of photographs are obviously not suitable for currently 
available photogrammetric cameras. 
Results of research work done in several institutions have clearly shown that the interior 
orientation problems of non-metric cameras can be overcome to an appreciable degree by using 
appropriate methodologies, and that some of the better non-metric cameras (such as Hasselblad, 
Rolleiflex SL.66, Linhof Technika, etc..) are capable of achieving the same accuracies reached 
using metric cameras (see, for example, Dohler, 1971[ 12]). Because of the rather large lens 
distortion in non- metric cameras (lenses generally designed for high resolution and image quality 
at the expense of image geometry), the data reduction should be done analytically, if accurate 
results are desired. 
2. Parameters of Interior Orientation 
In order to reduce metric data from the photography, it is necessary to reconstruct, 
physically or mathematically, the bundle of rays in object space. This can be done with various 
levels of sophistication, depending on the accuracy requirements in photogrammetric measure- 
ments and the data reduction approach (analogue or analytical). On one hand, one can use the 
simple classical approach involving only the reconstruction of the position of the interior E 
perspective center, as is generally the case in low accuracy analogue plotting. For the highest | 
accuracies, on the other hand, it is necessary to take into consideration radial and decentering 
lens distortions as well as the variations in lens distortion with focal setting and with object 
distance within the photographic field (Brown, 1971), ultra-flat glass plates are to be used in such 
cases, and advanced analytical solutions are performed. 
  
Definitions of the above mentioned parameters of interior orientation and other parameters 
identified primarily in connection with camera calibration are readily available in the literature 
(e.g. Manual of Photogrammetry [4]; and Carman [11] ). It might be appropriate to point out 
that some of the definitions given in these references differ somewhat from the definitions used 
in European literature (e.g. Roelofs [22] and Roos [23]). 
The various parameters of interior orientation are obtained through camera calibration, 
different approaches to which are discussed in the following sections. 
3. Close-Range Camera Calibration 
  
In contrast to aerialcameras, for which laboratory [11] and field [14] calibration 
procedures have stabilized over the years and for which standard procedures have been recommended, 
standard calibration procedures for close-range cameras are yet to be established. Optical 
laboratory methods involving the use of optical benches, goniometers, collimators, multi-collimators, 
etc.. are not suitable for close-range camera calibration since such cameras are focussed (in 
some cases focussable) at finite distances. Obviously, also stellar methods of camera calibration Y 
are not suitable for close-range cameras, unless provisions are made to have them focus at 
infinity. 
The lack of standard recommended procedures and the unsuitability of optical laboratory 
and stellar standard calibration procedures has led to the development of a number of ingenious 
approaches for field calibration of close-range cameras. In most of these methods, calibration 
is undertaken under real operational conditions, and thus yields realistic calibration for the total i / 
data acquisition system. 
  
A number of close-range camera calibration methods known to the authors are briefly 
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