10 
It is evident that the assumption that photographs 1 : 20,000 are used for plotting a 
1:25,000 map for densily cultivated areas is only valid for those areas for which a photo- 
interpretation for soils or forest is necessary. 
Where these photographs are not needed and the scale 1 : 70,000 cannot show suf- 
ficient details, the second coverage can be in a scale 1 : 30,000 to 1 : 40,000. The solution 
of the problem of passpoints for these photographs however, remains exactly the same 
as described for the photographs 1 :20,000 namely by means of the photographs in 
1 : 70,000. 
It must be kept in mind that this statement is based on the experience with aerial 
triangulation gained up till now and does not represent the maximum precision which 
may be obtained in future. This experience was first of all, with ordinary 9 X 9 inch 
photography without taking into account any influence of the irregular shrinkage of the 
film. Furthermore the question of the difference between stereocomparators and clas- 
sical analogue plotting machines is kept open. For the determination of height an im- 
provement is possible by the use of the combination of statoscope and airborne profile 
recorder. Unfortunately we do not yet know how much improvement can be expected. 
h. Conclusions. 
At the end of the foregoing section we came automatically from unmapped areas 
to highly cultivated and developed countries in which the mapping problem is the 
production of a large-scale topographic map. We found that the introduction of small- 
scale photography can solve the problem of the control points entirely. 
Especially in such countries, however, the question can be raised for which additional 
purposes these photographs 1: 70,000 can be used. We think at the production of small- 
scale topographic and geographic maps. We mentioned that in many of the old countries 
the usual method is to produce these small-scale maps 1 :100,000 and 1 : 250,000 by 
reduction and generalization of the maps on a larger scale. We believe, however, that 
it is necessary to consider in these countries the possibility to produce the small scale 
maps directly from small-scale photographs. Would it not be demanding too much from 
the military organizations of a country to wait for the map 1 : 250,000 until the base map 
1:25,000 is completed? Would it not be necessary to revise the map 1 : 250,000 in par- 
ticular in those countries with a dense population and a fast technical development, much 
more frequently than if we use for this only the maps 1 : 25,000? We have the impression 
at this very moment this process is going on in some countries. Yet we believe, that the 
possibility to use small-scale photography also to the benefit of a faster production of 
the maps 1 : 25,000 as mentioned above, has so far not been used. 
As a conclusion we may state that planning the survey of a country along the lines 
set out above, can speed up the map production and economize in many respects. A con- 
dition, however, is, that more research work is carried out, for instance in order to 
evaluate the resolving power of many of the existing plotting instruments. If we continue, 
however, to use instruments with anaglyph observation, it will be hardly possible to 
exploit thoroughly all possibilities of modern optics in wide-angle and super wide-angle 
cameras for the production of small scale topographic and geographic maps. Therefore it 
will be desirable to start the discussion about the research work as we believe this to be 
necessary at present. See for this No. AB1 of the I.T.C.-publications. 
ZUSAMMENFASSUNG. 
Planung im modernen Luftbildwesen. 
Es wird gezeigt, dass das Luftbild besonders wegen seines reichen Inhaltes uns ein- 
ladet festzustellen, für welche Zwecke und wie es verwendet werden sollte. Dies führt 
zu einer nationalen Planung für Kartographie. Die organisatorischen Bedingungen für 
eine gute Planung werden erwähnt.