which are to be presented during the Symposium at Delft, before the Congress. Further 
more ITC continued to take part in the international tests performed by OEEPE Comm. B 
(see III.4). 
Because of the difficulties of obtaining controlled blocks ITC has prepared an “artificial 
test block” which can serve as test material for the testing of various methods of strip and 
block adjustment [49]. 
D. Conclusion 
It is the writer’s opinion that the development in the Netherlands in the held of aerial 
triangulation is of great importance. It is the result of several services cooperating closely. 
The development is continuing and will yield further theoretical and practical results. 
The implications of the development for the work and the organisation of the services 
just start to be realized. The consequences are at present that the classical aerial triangula 
tion is completely abandoned in the Dutch Government services, as far as planimetry is 
concerned. It is expected that the same will be true in the near future also for heights. 
III. 4. Aerial triangulation carried out by Netherlands organisations 
A. KLM Aerocarto N.V. 
Aerial triangulation was carried out for several of the mapping projects mentioned in 
columns 7, 8, 9, and 10 of table 1. Until September 1962 the ITC-Jerie Analogue Com 
puter has been in use for block adjustment of the planimetric coordinates. After this a 
numerical variant of this mechanical system developed by KLM Aerocarto in cooperation 
with IBM has, in KLM Aerocarto’s organisation replaced the use of the analogue computer 
as far as planimetry is concerned. 
At an average of the scale of photography of 1 : 5,000 for mapping at a scale of 1 : 1,000 
the Jerie block adjustment gave the following mean square errors: 
minimum 
abs. rel. 
m x = 20 ¡am 15 ¡am 
m y = 18 ¡am 18 ¡am 
maximum 
abs. rel. 
m x — 50 ¡am 26 ¡am 
m y = 34 ¡am 32 ¡am 
For the large areas in Iraq mentioned in table 1, KLM decided to abandon for this super 
wide angle photography the aerial triangulation in analogue machines, but to apply the 
analytical method. For area A, for which only planimetric coordinates were required, 
radial triangulation was used. The first solution was possible, because the ITC was willing 
to carry out the measurements on its Wild Stereocomparator as can be seen from table 2 
and to deliver to KLM Aerocarto the computed strip coordinates. ITC proposed this 
procedure as it was interested in statistical material about regular production of stereo 
comparator measurements on super wide angle photography taken with a stabilized RC9 
camera. Strip coordinates were computed making use of Van den Hout’s method as 
programmed by Eckhardt for the Zebra computer. Also the connection of the adjacent 
strips was carried out on the Zebra by the same organisation. 
The block adjustment for planimetry was then computed by the new programme men 
tioned above, developed for electronic computing in one and two phases for the IBM 7090. 
All block adjustments for height were carried out by KLM using Jerie’s analogue computer. 
Regarding the super wide angle photography 1 : 60,000 (area B) the method of radial 
triangulation was developed and used as mentioned in III. 1. Al). KLM Aerocarto used