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convergent twin camera gave for a scale 1 : 500 excellent photography and satisfying 
results. 
This service used in general the Wild Autograph A 6 for the plotting 1 : 10.000, the 
Zeiss Stereoplanigraphs C 4 and C 8, the Wild Autographs A 5 and A 7 and the Santoni 
Stereosimplex III for plotting on larger scales. 
The model scale is chosen between !/, and 1/, of the scale of the map, depending on the 
type of camera and on the scale of photography. 
For the mapping of the coastal sand dunes in the scale 1 : 2.000 and 1 : 2.500 from 
negatives 1 : 8.000 a contourline interval of one meter or two meters is used, depending 
on the type of vegetation. The precision of all this plotting can be expressed by the tolerance 
which is set as a standard error of planimetry of 0,1 to 0,15 mm in the map. The standard 
error for altimetry is for contourlines 0,25 times the contourline interval and for spotheights 
0,2 to 0,4%/,, of the flying height. 
Field work is first of all the establishment of the signalization in the terrain. The signal 
dimensions are as follows: 
50 cm for 1 : 8.000 to 1 : 10.000 photography 
35 cm for 1: 5.000 to 1 : 8.000 photography 
25 cm for 1 : 5.000 and larger scale photography. 
These signals are also used to establish secondary control in the lateral overlap between 
strips and to use those points instead of transferred pricked points to lessen the preparation 
work in the laboratory whereas errors in point transferring are entirely avoided by this 
method. 
Regarding the methods for field completion surveys, this service makes use of an enlarged 
photo-copy of the plotted map as pencil drawing. Plotted details of sharp definition and 
the plotted position of special premarked points or beacons are used. 
When and where the organization renders it practicable the operator takes part in the 
preparatory field work — establishing ground control, signalizing etc. — in order to gather 
meanwhile an adequate information of the type of terrain and of its special features, all 
this being of use afterwards when plotting the photographs. In other cases, opportunity is 
given, before or pending the plotting, to pay a visit to the terrain and take notice of 
such details which might cause difficulties or mistakes when interpreting the contents 
of each model. 
Regarding the determination of coordinates we refer to cHAPTER III deling with aerial 
triangulation. 
The remarks made for the Survey Department of the Ministry of Transport and Water- 
staat are completely valid for K.L.M. Aerocarto as far as large scale mapping is concerned. 
The difference is only in the equipment: instead of Wild Autograph A 6 and Santoni 
Stereosimplex III, this service uses Autographs Wild A 8. 
TABLE 6 gives a general review of the methods of production of large scale maps. 
Regarding the other questions of Commission IV/1 it can be answered that, except for 
non-topographic purposes, no terrestrial photogrammetry is used in this country. 
The tendency of development in this period was a more frequent use of the very large 
scales 1 : 500, and even larger, on behalf of technical projects, such as for instance railway 
yards. An experiment to determine cross sections from large scale photographs 1 : 3.000 
failed, not because of the precision of plotting, but because of the vegetation. Even grass 
proved to be sufficient to spoil the precision of the photogrammetric survey. 
Furthermore we see that, in particular in the Survey Department of the Ministry of 
Transport and Waterstaat, there is a tendency towards the application of analytical aerial 
triangulation in order to have the universal plotting machines free for high precision plotting. 
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