20 
General Report of Commission IV 
SUBCOMMISSION IV/3 
Small Scale Mapping 
by T. J. BLACHUT. 
1. Introduction. 
The report on small scale mapping is divided into two parts: a short description of 
general development, achievements and trends in the field and a summary of the more 
important information obtained through the questionnaire distributed to all the countries, 
members of the International Society of Photogrammetry. 
In different countries the meaning of “small scale” may be different, e.g. in Europe 
the scales from 1 : 20000 down are regarded as small scales, whereas in other continents 
(i.e. in North America) often even such scales as 1 : 50000 are referred to as large. Since 
this classification is a matter of convention we decided to use the European definition. 
2. General development and trends in the field of small scale mapping. 
It is the task of Commission IV to gather and assemble the information pertaining 
to photogrammetric mapping of earth surface and to draw the conclusions, both economic 
and technical without recourse to detailed theoretical and technical analysis of the proce 
dures used. In consequence to give a proper review of the present situation and its recent 
developments and trends we must include elements, which may be dealt with in one of 
the other Commissions of the International Society of Photogrammetry. 
Small scale mapping problems can be sub-divided into two distinct groups: mapping 
of countries with an existing network of geodetic points and of those without it. To the 
first group will belong mapping operations in densely populated, developed countries 
with no major communication problems. Scales used in this case will be larger, rather 
1 : 20000 or 1 : 25000, than 1 : 50000. The mapping difficulties will be of economic rather 
than technical character and they can be summarized by the question — How to produce 
necessary maps in the most economic way and the final choice of the mapping procedure 
will be made first of all from this point of view. 
Small scale mapping of areas without even sparse geodetic network has an entirely 
different aspect. The main problem is technical and not economic. The question to be 
answered is: How to map the given area at all without recoursing to the classical proce 
dure, e.g. to the establishment of the relatively dense network of fixed horizontal and 
vertical control points using field surveying methods. Countries without basic geodetic 
network are mostly inaccessible, with very sparse or no communication facilities. They 
lie mostly in zones of difficult tropical or arctic climate. Under these circumstances, all 
attempts to establish a network of ground control points through the medium of ordinary 
field surveying procedures will encounter extraordinary difficulties and may meet with 
failure. 
In the field of large and intermediate scales the field of photogrammetric operations 
can be combined into one smooth mapping process. In small-scale mapping of remote 
territories the full advantage of photogrammetric methods can often not be taken because 
of insurmountable difficulties in establishing the necessary network of ground control 
points. Therefore, the recent achievements in this particular field seem to be the most 
important development in the field of photogrammetric mapping. These achievements 
were possible because of the introduction of various electronic techniques into photo 
grammetric mapping. 
Modern small-scale mapping starts with the establishment of a triangulation net.