Investigation zone taken as example of adopted methodology 
As example of the methodology application was taken into 
consideration a zone of Eastern Borneo (Kalimantan Timur) compri- 
sed among Siduong, Segah and Kelai rivers, which flow into each 
other in a single branch near the built-up centre of Tanjung Re- 
deb placed off the coast about 60 km. 
The examined zone, shown only in part in the herewith atta- 
ched map, covers a surface of approx. 625 km 2 and reveals itself 
to be hardly accessible. In fact, except from the navigable waters 
of Segah and Kelai rivers, only two penetration tracks exist, 
which will be mentioned afterwards with regard to the "Base Map". 
Few are the built-up centres on the riversides and the in- 
land is characterized by a thick vegetation, which hampers the 
interpretation of air photographs. 
First phase: preparation of Base-Maps 
  
Starting from the unchecked mosaic and proceeding with the 
photograms interpretation, 3 thematic maps were drawn-up to 
outline the characteristics of the zone into examination. These 
maps are determinant from the physical-environmental viewpoint and 
permit to verify the land-accessibility, in order to plan the 
campaign surveys on the basis of various ascertained difficulties. 
The 3 maps which will be shortly described afterwards and which 
represent the first work-phase (see table no.1) were respectively 
named: Base-map, Land-forms Map and Land-use map. 
a) Base-Map 
Failing a topographic map, it was necessary to draw-up a 
simplified plani-altimetrical map showing minutely the hydrogra- 
phic net, the watersheds and the most significant peaks. This 
work permitted to define the drainage density and to outline shape 
and dimensions of catchment basins. 
The location of the main peaks, which, given the particular 
soft morphology of the hilly area, are not too high, permitted to 
calculate approximately the difference in height between said 
points and the course of the rivers which mark the boundaries of 
this zone; keeping into consideration that the official measure- 
ments of these rivers are 7 mt. above sea level for Segah river 
and 16 mt. above the sea level for Kelai river, it was ascertained 
that the difference in height between the higher and the lower 
lands of examined area does never exceed 200 mt. 
In the same. map are shown also the communication lines, 
which, apart from the possibility to utilize navigable waterways, 
are actually limited to two tracks: the first crossing the area 
North-South from river to river and the second departing from 
East and penetrating inside the forest about some tens of km. 
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