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Line parallel to X-axis *\ 
Line parallel to Y-axis 
2} 
Object Space 
Coordinate System 
  
Line parallel to Z-axis 
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Figure 2 
Points Ry» Dy and n, are the respective vanishing points of the X, Y and Z 
2 
object space coordinate axes. They play a significant role in the solution of the elements 
of the interior orientation and exterior orientation matrix. 
Not only is ny the vanishing point of the X-axis, but it is also the vanishing 
point of any line parallel to the X-axis. Indeed, if a family of lines parallel to the 
X-axis is imaged in the photograph, all line images will converge toward and terminate 
at ny The same applies to ny and n, that is, n. is the vanishing point of any líne 
parallel to the Y-axis, and n, is the vanishing point of any line parallel to the Z-axis. 
Z 
The images of all lines parallel to the Y-axis will converge toward and terminate at ny» 
and the images of all lines parallel to the Z-axis will converge toward and terminate at 
n, 
If ny is the point at which a line through the camera station directed parallel 
to the X-axis intersects the photograph, then its coordinates can be obtained directly 
from the collinearity equations. For any line through the camera station and parallel to 
the X-axis, Y = Yo and Z = Ze Hence, for any object point, I, on this line, (Y, - Yo = 0 
and (Z, - Ze) = 0, and the image coordinates of I become: