10 
A. Analytical aerial triangulation 
The theoretical foundation and the development of the main computer programmes 
(Stantec Zebra ITC) for the method of analytical aerial triangulation according to the 
method of Van den Hout, have been achieved in the period before 1960. Van den Hout 
(Rijkswaterstaat and ITC) has reported about it during the Analytical Conference Week 
in Milan, 1960 [40]. In completing this system of analytical aerial triangulation during 
1960-1964 a number of additional computer programmes have been developed at the 
ITC, concerning for instance the use of réseau photography and correction for earth cur 
vature, see [5], [6]. A major extension has been developed by I. Levy (ITC) who has 
worked out a very general computer programme for analytical aerial triangulation which 
can incorporate measurements both from analogue projection instruments and stereo 
comparators [53]. Special care has been taken to correct for known instrumental and image 
errors. A textbook representation of analytical photogrammetry has been given by F. 
Ackermann (ITC) [4]. 
The further contributions to the theory and practice of aerial triangulation are mainly 
concerned with adjustment procedures or they have been developed in connection with them. 
B. Adjustment procedures. Analytical block adjustment procedures 
In 1960/61 F. Ackermann (ITC) developed a method of least squares strip adjustment 
following the well-known approach of Vermeir and Baetslé. The method has been worked 
out for height adjustment and planimetrie adjustment separately [1]. It has been pro 
grammed for the Zebra computer by H. F. Soehngen, and is since in practical use. Exten 
sion to the simultaneous adjustment of x,y, and z-coordinates is developed and has been 
studied by G. C. Agarwal (Thesis ITC), but is not yet programmed. 
The well-known ITC-Jerie Analogue computers for block adjustment about which 
H. G. Jerie has reported at the Analytical Conference Week in Milan 1960 [44] have been 
subject to further operational research and extensions: I. Levy has worked out a computer 
programme (Zebra) for a semi-analytical procedure which takes care of all numerical 
computations involved in the ITC-Jerie analogue method of planimetrie block adjust 
ment [52]. The planimetrie analogue computer has been modified to incorporate scale 
information from APR data. An extra analogue computer has been developed to adjust 
azimuth data in blocks with cross strips, see [47]. 
The problem of analytical block formation and block adjustment was tackled from two sides: 
In the group TH-KLM a set-up for planimetrie block adjustment was developed by 
Sonnenberg working with independent models. Later on M. Tienstra developed a proce 
dure for height adjustment of a block following an idea of C. M. A. van den Hout, also 
working with independent models. Both approaches have been programmed by IBM. 
In the group ITC-Rijkswaterstaat it was C. M. A. van den Hout who made an approach 
for planimetrie block adjustment with independent models. He made special use of the 
linearity of the system of unknowns and the occurrence of many zeros in the coefficient 
matrices of the normal equations. A short description of the method was given by Van den 
Hout during the Munich Photogrammetric Weeks, 1963*. This approach was taken up 
at the mathematical department of the ITC and worked out into a computer programme 
(Zebra) of great flexibility. 
* H. Kasper, Bericht über ein neues ITC-Verfahren für die rechnerische Blockausgleichung nach der 
Methode der kleinsten Quadrate, Schw. Zeitschr. f. Verm. 1964, 1.