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and small. Medium and small models are specially convenient for the establishment of 
ground control points using precise traversing or measuring sides in the triangulation nets. 
The picture of changes which follow the introduction of electronics to photogram- 
metric mapping would not be complete if we did not mention electronic computing machi 
nes. It is obvious that all large computations are greatly facilitated by the use of elec 
tronic computers. These make it feasible to introduce analytical methods to photogram- 
metric mapping operations. 
As already stated the establishment of ground control points by photogrammtric or 
other means solves the major problem of small scale mapping and the mapping of remote 
areas in particular. This is not to say that the detailed plotting operations are less im 
portant and that they can be neglected. On the contrary, field work, aerial photographic 
operations as well as the instrumentation and the execution of the detailed plotting must 
be carefully studied and planned to make the mapping operation a success. 
With regard to the type of aerial photographs two tendencies must be recorded: use 
of convergent photographs and the replacement of present wide angle photographs (field 
angle about 90°) by super wide angle photographs, with the field angle of over 120°. 
The first tendency became quite popular in the United States of America. The main 
argument used in oblique photographs is the gain in accuracy as well as in economy due 
to the larger ground coverage by single photographs and by pairs of photographs. In 
consequence, the number of overlaps required to cover a certain area is much smaller than 
if usual vertical photographs are used. The resulting economy is twofold: economy in 
field work and in the office work. 
Inconveniences of symmetrically convergent photographs include the impossibility of 
using unrectified convergent photographs for production of mosaics, the detailed plotting 
with simple plotting devices and difficulties in photo-interpretation etc. 
For all these reasons, another group of photogrammetrists favors retention of ver 
tical photographs but replacing in the field of small scale mapping usual photographs by 
super wide angle photographs. 
The increase of base ratio will also increase the plotting accuracy. In consequence, to 
meet given accuracy specifications it will be possible to use the photographs made from 
higher flying height or in smaller scale. Vice versa - photographs in a given scale may 
be obtained from the lower flying heights. This represents a certain economic and opera 
tional advantage. (We cannot refrain from remarking that vertical-oblique photographs 
already proved successful in large scale mapping would combine the advantages of both 
systems and at the same time eliminate some of the disadvantages). To close our remarks 
on photographic part of mapping operation it should be mentioned that more attention 
has been paid lately to infrared photographs. This is true not only with the special appli 
cations mentioned above but also in vertical photography. Infrared photography is useful 
in tropical countries where atmospheric haze presents diffculties. 
As to the detailed plotting, it seems that the general accuracy requirements have 
been tightened, particularly in the countries where the maps were made “as good as it 
was possible”. Highly developed countries have also reached a high degree of perfection 
and automatisation in map production from the field operation to the final printing. As 
never before the map becomes an industrial product. The production process is split up 
into single simple operations and the number of persons aware of all steps and techniques 
involved is lesser and lesser. 
In European countries contact glass diapositives are mostly used for detailed plotting 
on second order plotting machines. An optical system provides a view of diapositives under 
strong magnification. In the countries with Multiplex as the basic detail plotter there is 
a general trend to increase the size of diapositives or even to use as the plotters ana- 
glyphic equipment which takes the size of the original photographs. In the field of recon 
naissance mapping, new simple devices are produced which through the medium of built- 
in mechanical computers allow for relative and absolute orientation of the photographs.