8 
and Waterstaat added two more Stereosimplexes III, bringing the number of precision 
and universal plotters of this service to 6. The coordinate registration EK 5 was added to 
the Wild Autograph A7 of this service. 
KLM Aerocarto sold its Wild Autograph A7 K to Wild because of very little or no 
use for this instrument for convergent photography in this organisation, and purchased 
one Wild Aviograph B 8. The Survey Department of the Ministry of Transport and Water 
staat sold its Wild Autograph A5 of 1938 to a foreign private organisation. 
The International Training Centre for Aerial Survey improved its collection by pur 
chasing three topographic plotters, viz. the Wild Aviographs B8 and B9 and the Kern PG 2. 
Kern will replace this instrument, delivered in 1962 with the improved model, now under 
construction. Regarding instruments with direct optical projection the ITC obtained the 
Bausch & Lomb Ballplex with three projectors of the latest model. 
Furthermore the ITC has paid great attention to the development of the analytical 
methods. The Stereocomparators of Hilger & Watts and the Zeiss Stereocomparator were 
delivered in 1963 and 1964; the delivery of the Nistri comparator of the latest model can 
be expected in August 1964. As complement to the Stereocomparators the ITC bought in 
this period the Stantec Zebra Transistorized Computer of the Standard Electric Comp. 
Regarding third-order instruments the ITC obtained a second Galileo-Santoni Stereo 
micrometer of the latest model with the possibility for rectifying [170]. 
Dr. Jerie designed a new type of very simple third-order plotting instrument which is 
intended for very small scale mapping. It has been sent to the Topographic Service of 
Canada in Ottawa for testing and comparison with a similar instrument developed by 
R. Moore. 
Regarding use and testing of instruments the study of the dynamic performance of 
plotting instruments by Dr. B. Makarovic of ITC should be mentioned. This study deals 
with the conformity of straight lines and curves between negative and map under the 
influence of the movements during plotting. This new method to disclose certain qualities 
of a plotting instrument will be described in an invited paper for the Lisbon congress and 
later on in more detail in an ITC Publication. 
CHAPTER III. AERIAL TRIANGULATION 
ill. 1. General introduction 
Aerial triangulation is the most important subject in photogrammetry. This is not only 
true from a theoretical viewpoint, but also with respect to the practical application to all 
kinds of mapping problems. It is not surprising that the Netherlands photogrammetrists, 
still following the pre-war tradition in this country, have paid their main attention to all 
aspects of the problems of determination of minor control points. 
Regarding the theoretical development in the field of aerial triangulation it is not an 
exaggeration to say that the period 1960-1964 has shown more activity and more progress 
than ever before. This development was made possible through the close cooperation 
between photogrammetrists (Van den Hout, Ackermann, Jerie, Van der Weele) with 
mathematicians (Eckhardt, van Leyden) understanding each other’s language and methods. 
Parallel to this ITC group we mention another group of photogrammetrists of the Geodetic 
Institute of the Technical University (Roelofs, Sonnenberg and KLM Aerocarto) with the 
mathematical organisation of IBM. The results of the developments which will be described