power of the modern Aviotar is much better than the pre-war lenses used for photo- 
graphy on the same scale (1 : 20.000) for the same maps (1 : 25.000). The application 
of the rectifier to our map construction is not favourable to the use of the wide-angle 
lenses. The tolerance for the difference in height in the terrain would only be a few 
metres and the result would be that a much larger area than from the standard angle 
photography must be plotted in stereoplotting instruments instead of restitution by 
means of rectifiers. Such a decision would have meant a very important change in 
equipment and would have caused an unacceptable delay in the production of the 
maps. Therefore wide-angle could not be accepted. 
The Topographic Service also considered the possibility of using air photo- 
graphs in a scale of 1 : 30.000, made with the standard angle Aviotar f — 21 cm. 
With this scale the closing errors in the radial triangulation and the residual errors 
in rectification increase to such an extent that they surpass the acceptable tolerances. 
Furthermore, we believe that, although the resolving power of modern lenses is better 
than of pre-war lenses the general usefulness of a collection of photographs of the 
whole country in a scale of 1:30.000 is much smaller than for photographs 
1 : 20.000; consequently the use of the same photographs by other agencies, even for 
large-scale plotting up to 1 :2.500, strengthens the decision of the Topographic 
Service not to change the scale of its photography. 
The deformation of the film, caused perhaps by a lack of flatness, has been 
reduced by special measures taken by KLM Aerocarto, The difference between film 
and plate cameras, in particular for large-scale plotting, remains however, so con- 
siderable that all photography in the Netherlands in the scale of 1 : 10.000 and larger 
and also part of the photography in the same scale outside the country, has been 
carried out with the Wild RC 7 plate camera f — 17 cm. It may be true that sometimes 
the film gives excellent results. We, in the Netherlands, do not consider this as evidence 
that the film camera is equivalent to the plate camera. In order to obtain this 
evidence it would be necessary to have films which always give good results; this. 
however, will be very difficult. 
The glass negative is not perfect either. The International Training Centre 
for Aerial Survey has tested samples of batches by using an optical flat in connection 
with a sodium vapur lamp. The interference pattern gives contours of equal deviations 
and this has shown that maximum values of 0,04 mm are exceptions, 0,03 to 0,04 mm 
occur in a few cases, 0.02 to 0.03 frequently, 0.01 to 0.02 frequently and smaller 
than 0.01 only rarely. Errors of 25 microns in a wide-angle camera cause displace- 
ments in the position of a point on the negatives which are larger than is in 
accordance with the precision which can be obtained in our present restitution 
instruments. If the plate is not better than this, then the difference with film is 
rather small. If we do not employ restitution instruments with the Porro Koppe 
system in which we use original negatives and not diapositives, the tolerance for 
flatness should be no more than 20 microns. So far we must admit that the glass 
plates we have used in the Netherlands, have not fulfilled this requirement. 
Furthermore it may be mentioned in this National Report that several tests 
and comparisons have been carried out during this period which all show that today