SS c E a 
To overcome these disadvantages, the arrangement shown in Fig. 5 was devised. Oculars 17, 
for the left eye and 18, for the right eye are provided. The ray path for the left eye passes 
through a five-sided prism 19 and is deflected through a total angle of 22.59 downwards to 
the lower strip 16. The ray path for the right eye passes through a similar prism 20 and is 
deflected by 22.59 upwards to the upper strip 15. The working table 14 is so arranged 
that the strip 16 lies horizontally while the upper strip 15 lies at an angle of 45° to the 
observer. 
A stereoscope designed according to this principle is now being produced, under licence, 
by Wild Heerbrugg. It has been given the name ,, Wild ST10 Strip Stereoscope'*. 
Stereomaps — a new aid for the planner ... 
Consider as an example aerial photographs taken as for normal mapping with the strips 
lying in the East-West direction. If the aerial photographs are cut in halves and oriented 
strip by strip in the device the observer has a 3-dimensional map in front of him, of a strip 
of terrain which may be as long as is required and practical. I call this a ,,stereomap'*. 
If the strips are copied photographically the following advantages exist: 
1. The preparation of the Stereomap is quick and cheap. The work is simple and easy 
to learn. 
2. Storage is simple, being similar to that of map sheets. 
3. The stereomaps are ready oriented and always ready in a moment for stereoscopic 
observation. 
4. The image quality of the stereomodels is good. 
5. The use of the stereomaps and of the stereoscope is very simple and rapid. 
6. The planner can show the results of his work directly in the stereomap or, for example, 
in an orthophoto-map. 
7. In an unmapped or badly mapped terrain the stereomap gives an extraordinarily rapid 
map since it gives an extremely good picture of the whole terrain. 
8. The stereomap can be made from enlarged parts of the photographs also. 
. .and for the interpreter 
The advantages outlined above are valid also for the interpreter and lead me to predict that 
stereomaps, bringing a miniature model of the terrain onto the table of the planner or 
interpreter, will be widely used in future, either as a by-product of normal mapping or 
specially produced for the purpose. The importance of stereomaps — from any arbitrary 
type of aerial photography — is perhaps even more important for interpretation than for 
planning, since the continuous spatial observation of a wide terrain possibly offers new 
possibilities in interpretation.