It is worthwhile to mention that the experience gained with the I. T.C. Jerie block ad- 
justment has shown to be time-saving for the absolute orientation. The very high relative 
precision reduces the discrepancies between models in adjacent strips and also in each 
model itself to negligable amounts and speeds up the absolute orientation. In some cases 
a reduction of an hour per model was obtained. Since the cost of one hour absolute orienta- 
tion includes in many cases the cost of a photogrammetrist, a draughtsman and in addition 
the amortisation cost of an expensive plotting machine it is obvious that this amount alone 
approximately equals the total cost per model of the block adjustment for planimetry 
Subcommission IV|2. City Surveying 
In this country no photogrammetric survey of cities was carried out. The only effort in 
this direction has been the participation of the I. T.C. at the "Essai controlé" organized 
under the supervision of Mr. Dubuisson. City surveying and also the cadastral survey of 
terrain of Class I, require a precision which cannot be met by photogrammetric means 
due to the small parcels which always occur in these areas. 
Subcommission IV/3. Production of topographic maps on medium and small scales 
The service in charge of this type of map production are: 
1. The Topographic Service of the Ministry of Defence. Mapping of the regular to- 
pographic maps of the Netherlands for Military and Civil purposes on scales 1 : 10.000, 
1 : 25.000, | : 50.000 and 1 : 100.000. 
2. K.L.M. Aerocarto Ltd., Schiphol. Delft. Contractors for airphotography and map 
production everywhere. 
3. Survey Department of the Ministry of Transport and Waterstaat (Meetkundige 
Dienst) at Delft. Production of topographic maps for technical purposes, in particular 
for Government Agencies and for the Royal Dutch Shell Group on scales between 
] : 20.000 and 1 : 100.000. 
We have been provided with information from the first two agencies. We will mention 
in detail the production of the Topographic Service and will combine the Survey Depart- 
ment of the Waterstaat with K.L.M. Aerocarto. 
IV/3.a. The Topographic Service of the Ministry of Defence 
Regarding photography and aerial triangulation we have given full details in the CHAP- 
TERS I and III and do not have to repeat those here, except for a few particulars. 
The plotting scale for the flat part of the country, which is the scale of the rectified 
diapositives, was originally 1 : 16.666. This is 2/; of 1 : 25.000. In the last few years it 
was decided to also accept the 1 : 10.000 map as a regular map of the country. Then a 
scale of the manuscript of 1 : 12.500 was chosen in order that the map should be derived 
as a moderate enlargement from the manuscript. 
In our 1956 report it was mentioned that the experiments with the scale of photography 
1 : 30.000 were already abandoned. The development of the wide and super-wide-angle 
high precision lenses has however stimulated the Topographic Service to study again the 
question whether it is justified in reducing the scale of airphotography from 1 : 20.000 to 
1 : 30.000 by using Aviogon lenses instead of the Aviotar. A clear answer to this problem 
has not yet been obtained. This means, that what was clear in 1956, now seems to be 
doubtful again. We consider this an understandable development. Another step to increase 
the economy would be the acceptance of the 9 x 9 inch size of the negatives. This would 
26