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of planners, and many potential users are not yet convinced, or aware, of 
its qualities. Informing the potential users is, therefore, a first task. 
Since the use of photo maps and orthophoto maps has found a certain 
foothold in planning practice, users will be better able to specify the type of 
product they want. It is likely that there will be a development towards two 
clearly separated products: on the one hand the crude photo map (just a 
rectified and enlarged very recent photograph, screened and with topographic 
co-ordinates added), on the other hand a refined orthophoto map, maybe even 
to be interpreted in stereo, approaching the qualities of the topographic line 
map but produced faster and more economically. 
4.2 Hardware Development for Photo-Interpretation 
Optical Mechanical Instruments 
It seems that one must be rather pessimistic about the interest shown by 
industry in the development of practical interpretation instruments. Unlike 
photogrammetry, urban photo-interpretation does not benefit from sophis- 
ticated hardware since it cannot boast of highly trained operators. Interpreters 
are interested in easy-to-handle instruments, not causing irritation and strain 
by unnecessarily complicated design. Most instruments produce complaints 
about their ergonomic situation (instrument height, looking angle, head 
support etc), image illumination, size of exit pupil, ocular adjustment during 
image scanning, room for manouevering images and maps, separate Ax and 
A y adjustment when double-scanning, range of optics for people with spec- 
tacles etc. The selling potential of an appropriate interpretation instrument 
is much higher than that of a photogrammetric plotter; still, it is difficult to 
recommend to potential users tools other than the pocket and mirror stereo- 
scope. 
Instruments for Electronic Data-Processing 
Where interpretation data are to be entered into urban data bases, 
electronic data-processing becomes a necessity. After a period of experimental 
set-ups, such as the projection/grid-digitising method developed by BDPA in 
France, a new generation of special equipment might be expected, in which 
photogrammetry, photo-interpretation, digitising, and some pre-processing 
will be integrated. Such equipment has already been commissioned by the