Se ni 
Mathematical Definitions 
      
Physical Definitions 
  
(Rays): 
The straight lines passing through the 
projection center. 
Principal rays: 
The light rays passing through the entran- 
cc pupil center. 
  
Principal point H': 
The foot of the perpendicular from pro- 
jection center O on the image plane. 
Principal point H': 
The point of penetration of that principal 
ray through the image plane whose object- 
side part, if linearly extended, is perpen- 
dicular to the image plane. 
In the case of rotation symmetry, this 
definition supplies the center of sym- 
metry in the image plane, in the case of 
freedom from distortion, the definition 
furnishes the base point of the perpendicu- 
lar from the projection center on the 
image plane (corresponding to the ma- 
thematical definition). 
The frame fiducial marks of the photo- 
grammetric camera are so adjusted as to 
cause the fiducial center M' to coincide 
with the principal point H’. 
  
Principal object axis: 
The straight line passing through project- 
ion center O and principal point H’. 
(Radial distances 7’) : 
The distances of the points of penetration 
of the rays passing through the image 
plane, from the principal point. 
Principal object axis: 
Coincides with the object-side part of that 
principal ray which passes through the 
principal point of the image plane. 
Radial distances 7’: 
The distances of the image points lying 
in the image plane, from the principal 
point. 
  
(Object angles c) : 
The angles between the principal object 
axis and the rays. 
Object angles 1: 
The object-side angles between the prin- 
cipal object axis and the principal rays. 
  
(Image function) : 
The analytical relation between the object 
angles v and the corresponding radial 
distances 7’. It is given by the tangent 
function: 
v =c¢.tan 7. 
Camera function: 
The analytical relation between the object 
angles 7 and the corresponding radial dis- 
tances 7” assigned by the optical project- 
ion, 
In the case of rotation symmetry, this 
relation may be represented by the for- 
mula: 
7 ue. Fr). 
In the case of central projection, this 
general relation is translated into 
1” = e, . tan 7. 
Image function: 
The relation between the object angles and