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The schematic sketches heading each column indicate the two different conceptions 
on which these definitions are based. At the top of the left-hand column, the geometrical 
central projection is represented from which the mathematical definitions derive. The 
physical definitions, on the other hand, only use the relation between the object-side prin- 
cipal-ray bundle and the image points, without regard to how this arrangement comes 
into being and which quantitative law it follows. To show this is the purpose of the 
sketch heading the right-hand column. 
Of the mathematical definitions, some concept designations are in parentheses. 
Ordinarily, these definitions are not expressly specified, because they either go without 
saying or are not needed. That they are nevertheless stated is only in order to show 
their analogy to the corresponding physical concepts. The more conspicuous therefore is 
the absence of the concept “distortion from the mathematical definitions. Its presence 
constitutes one of the most essential differences between the mathematical and physical 
definitions. 
TABLE OF CONCEPTS 
Mathematical Definitions 
Physical Definitions 
  
  
Fig. 1 
EP 
bo 
x 
| ig 
Fig. 2 
  
(Image plane) : 
The plane B indicated in the above sketch 
by its trace in the plane of the drawing. 
(Origin of Coordinates) : 
The zero point of a right-angled coordi- 
nate system lying in the image plane B. 
Registering plane : 
The plane of the registering frame of the 
camera. : 
Image plane: 
The practically plane surface in which 
the photographic image is generated, and 
which should coincide with the registering 
plane, 
Fiducial center M': 
That point in the image plane which is 
determined by the images of the frame 
fiducial marks. 
  
(Projection center): 
The point O in the above sketch. 
Projection center O: 
The object-side projection center of the 
camera (termed also for short project- 
ion center) is the center of the lens 
entrance pupil. 
The image-side projection center of a lens 
(which lies in the exit pupil center) ordi- 
narily plays no part in photogrammetry. 
The expressions ,entrance pupil” and 
»exit pupil” refer to the arrangement in 
taking. They are used without alteration 
in reconstruction.