hy, 
| com- 
in the 
tation 
rect or 
aerial 
on are 
Conse- 
e than 
4. 
ation of 
ns have 
rision of 
on with 
  
aerial photogrammetry to the extent that it concerns the principles of the 
plotting procedure. 
But as soon as we start to determine with the theory of errors the real ac- 
curacy of terrestrial and aerial photogrammetry, we find that the problem is 
very similar in both cases. Up to now, however, the theory of errors of terrestrial 
stereophotogrammetry does not seem to have been treated to the same degree 
as aerial stereophotogrammetry. In particular the error propagation within the 
photogrammetric model as a function of the errors of the elements of orientation, 
before and after an adjustment of discrepancies in control points, has not been 
completely treated in any one of the existing textbooks. Therefore there will be 
i d some of the main principles which are of interest in this case; also the 
discusse 1 : 
principles will be applied to a practical experiment. 
For the introduction to the problem, and with the aid of some illustrations 
  
  
Fic. 1.—The principles of terrestrial photogrammetry. The photography. 
Some elements of the inner and outer orientation are indicated. 
there will be briefly demonstrated the general principles of terrestrial photogram- 
metry. 
In Figure 1 the feature containing the points 4 and B is photographed from 
the stations O; and O,. 
The inner orientation of .the cameras—the principal point, principal dis- 
tance and the distortion—is known from the camera calibration; the outer orien- 
tation—the three coordinates x, y, 2 of each exposure station, the two angles 
and w which determine the direction of the camera axis and the angle x which 
determines the location of the pencils of rays around the camera axis—is deter- 
mined in connection with the photography. 
Figure 2 shows the general principles for the determination of the coordinates 
of the point P,. 
. The rays towards Pi from the two stations can be reconstructed from the 
mage coordinates of the points P;' and P;". From the left picture we obtain 
the angles o and B: which determine the ray O;P;' from the coordinate plane 
às: 
- 
SR ALLE 
  
SYMPOSIUM—NON-TOPOGRAPHIC PHOTOGRAMMETRY 85