Apart from these units, however, much more geomorphological data can be
indicated.
With these desiderata in mind, the ITC System was devised as an analytical geo
morphological survey method and thus morphometrical, morphographical,
morphogenetical and morphochronological aspects of land forms are included.
Attentmn is furthermore paid to lithology and processes. Whenever possible the
System is concurrent with survey methods and legends developed earlier so as to
benefit from experiences gained in various countries.
Aerial photo-interpretation is the starting point of the survey. A first approach
to the survey is through rapid scanning of the photos.
Aerial photographs, being a detailed recording of the land surface, greatly in-
crease the efficiency of geomorphological survey and it can therefore be said with
justification that geomorphological survey without the use of aerial photographs
(in conjunction with fieldwork and laboratory investigations) is obsolete. Aerial
photographs cannot only be used for the preparation of an adequate topographic
base for the geomorphological map, for planning the field work, for detailed posi-
tioning and exact plotting of observations in the field etc., but above all they permit
a quicker and more precise geomorphological survey because the geomorphological
phenomena appear on the airphotos in their exact shapes and patterns. Further
more morphometric information and also a good deal of lithological data can
easily be obtained.
The maps prepared include a general purpose ('pure') geomorphological map,
a morpho-conservation map and a hydro-morphological map. Lithology is thought
to be of importance for all these maps and thus it is combined with the (grey)
topographical base (including contour lines) and used for three maps simultane-
ously. This is a considerable saving in cost and time. The hydrographic network
is preferably printed in blue but can also be put in black if simpler map reproduc-
tion is desired.
The general-purpose map stresses morphogenesis and chronology. The best
cartographical means; coloured area symbols are used for major genetic landform
types. When, however, lithology is really of prime geomorphological importance,
it is incorporated in the legend e.g. by introducing units such as 'granitic residual
hilf, 'sandstone cuesta' etc. This will render it possible to indicate these particularly
important lithological data with coloured area symbols; otherwise only the grey
dry transfer symbols will be used for the type of rock.
Because slope classes for a general purpose map are only of minor importance
and also to reduce printing cost, no various hues of the coloured area symbols
are used, nor is a transparent overlay produced. The slope classes, however, are
indicated by coloured area symbols in the morpho-conservation map because for
that purpose they are of prime importance.
Minor genetic landform types and also processes are indicated by line symbols
for which only the black colour is used so as to simplify the mapping system.
The chronology is indicated by a lettering in black and no colours are applied
for them. This is to render it possible to simply omit the chronology of features of
uncertain ages. It is not considered good practice to represent chronology by
differently coloured line symbols as this would greatly increase printing cost and
also would imply that the age of all features indeed must be known.
Inlroduclion to the ITC System of geomorphological survey
89
K.N.A.G. Geografisch Tijdschrift IV 1970) Nr. 1
