6 
Photogrammetric instruments of various kinds can be demonstrated in 
a very clear way as soon as stereoscopic pictures are available. The 
training of the stereoscopic vision has proved to be of great value for 
the later work in various instruments. 
The Mirror Stereoscope and Parallax Bar 
This simple instrument has proved to be of great value for the basic 
and advanced photogrammetric instruction. Particularly the measure- 
ments of y-parallaxes with the parallax bar is of great value as an in- 
troduction to the theory of errors and to the training in ordinary photo- 
grammetric plotters. 
Normally, excellent results can be obtained from parallax measure- 
ments for the determination of the orientation data and elevations on 
the ground. This fact creates great confidence of the students in the 
possibilities of the photogrammetric procedures. 
Also in terrestrial photogrammetry the mirror stereoscope and paral- 
lax bar is used for parallax measurements, particularly for deformation 
measurements and for the determination of differences between pictu- 
res in general. 
Multiplex for field survey camp use 
A multiplex equipment for field survey camp use (fig. 2) has been 
constructed at the Division of Photogrammetry and has proved to be 
of great value for the field practice. The students can perform the 
entire plotting procedure during the field practice period, check that 
the control points are visible and suitable etc. 
The multiplex equipment consists of Zeiss’ projectors and a special 
frame. The instrument can be packed and transported in a comparati- 
vely small wooden box (fig. 3).