2.2.4, Accuracy of Current Stereometric Systems 
  
As noted in Section 2.1., the use of stereometric cameras 
has, in general, been limited so far, to fields involving low 
and medium precision. An indication of the accuracy (mean 
square coordinate errors in object space) to be expected in an 
analogue stereometric system based on the ZEISS SMK photography 
is given in Figs, 11. The values shown in Figs. 11 are based 
on optimum condition in both the data acquisition and data re- 
duction systems. The axes X, Y, and Z referred to in the Figs. 
11 correspond to the coordinate system shown in Fig. 12. 
It should be noted that the left camera axis (camera L in 
Fig. 12) is chosen as the Z axis in the stereometric camera 
coordinate system, rather than the Y axis as generally adopted 
in photogrammetric literature on stereometric cameras. This 
deviation is mainly a matter of convenience, and is based on 
the following two reasons: 
To enable the use of the theory and computer programs 
developed for aerial photogrammetry without need for 
modifications and possible confusion. 
In most of the stereometric applications at the 
University of Illinois, the stereometric camera is 
used with its camera axes pointing vertically 
downwards. 
2.2.5. Use of Stereometric Systems in Fields of High Accuracy 
Requi rements 
2.2.5.1. Efforts Using a Standard Stereometric Camera 
  
Because of the attractiveness of the stereometric camera