Preface 
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The publication of this article by Prof. Jerie gives me a great deal of satisfaction 
because it illustrates the continuation of the effort to fulfil the task Tor which 
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the ITO was established, numely to pronote the application of aerial survey in 
development programmes for the benefit of the new nations in particular, and mankind 
in general. 
This has been realised in the past Tew years by developing sophisticated mithematical 
methods for the determination of minor control points. This resulted in the well known 
Anblock method for planimetric block adjustment, an analytical method for height 
adjustment and, more recently, the analytical block adjustment ia space as the closing 
link in the chain of applied mathematics in photogrammetry. The ITC staff has, 
however, always kept in mind that their methods should be applicable to practical 
surveys, anà not be restricted to pure scientific games without any purpose in mind, 
Àn example of this is the development of the ITO-Jerie Analogue Computer for Block 
Adjustment, which has so far been of more importance to developing countries, due to 
its simplicity and low investment cost, than the creation of sophisticated adjustment 
methods. 
In this article, Prof, Jerie again shows his understanding of the needs of these 
countries for an efficient mapping programme, which is generally hampered by low 
financial resources. The proposed system reminds me of a statement I used to make in 
my lectures at the ITC, namely never forget that by saving one dollar to-day you will 
be able to spend two dollars in 10 years time. This means that especially in poor 
countries, there is no sense in seeking perfection in scale in scale or quality that 
is not required at present. 
Consequently, a system should be programmed which would allow future improvements, 
but would not make the present products obsolete. 
Even though it will be difficult, it is obvious that, especially in developing 
countries, the mapping organisation must be advised by & department of economic 
planning of the areas which must have priority in the completion of the mapping 
programme (phase B). 
I welcome this article wholeheartedly and recommend its study and discussion to all 
former ITC students and to those responsible for planning mapping programmes in 
developing countries. 
W. Schermerhorn 
May, 1968