oints:
E 6)
(7)
(8)
from :
(9)
cions
^ this
ne
ated
dient 8 %
ent.
12
"8
2
Traverse AB, gives the shortest connection between road points
l and 12. Its total length is 1041 m. with gradients between
- 8% and + 8 % (see table 1). If for example a route had been
selected with a constant gradient, then the road would have
been much longer. Tracing AB, (see fig. 3) is 1275 m long with
a very gently gradient of approximately 1 %.uphill.
Such profiles of alternative traverses allow a comparison between
section lengths, gradients, obstacles, etc. before a field check
is carried out. An analysis of the cost for the construction of
the roads, and the cost for the transport of the timber by trucks
is necessary in order to decide upon the most economic route.
Only the best traverse is interpreted in detail on the aerial
photographs and tested out in the terrain
Conclusion
The procedure of road design and profile construction is very mich
simplified when carried out with the help of large scale topographic
mans or orthophotomaps with contours. Unfortunately such maps are
often not available in less developed countries, and their construct-
ion may be impossible because of lacking funds or facilities.
In view of the great need for improving the infrastructure of so
many forested areas aerial photography provides a relative cheap
means to obtain the desired information for the planning of a
road network, The aerial photographs should have a scale not
smaller than 1 : 15,000,in order to allow sufficient discrimination
between ground and forest canopy. The photography should be taken
with a minimum on tip and tilt, so that rectification is not
necessary. Through parallax measurements under a mirror stereoscope
it is possible to design a road system,zeven in steep terrain.
The techniques proposed in this paper allow a skilled ifterpreter
to draw up a well documented proposal for the layout of a road
network, that serves the multiple interests of the forest manager.
Literature
Chandra, R., 1976. Accessibility in tropical forests.
Working paper on accessibility studies.
FAO meeting, Rome.
FAO, 1976 Reports on accessibility of tropical forest
resource surveys. Nr.1, Madagaskar; Nr. 2,
Argentina; Nr. 3, Gabon.
Hallert, G, 1976 The application of aerial photointerpretation
to road design in Sweden.
ISP congress, Helsinki, 1976.
Le Ngoc Quy, 1971 Aerophotogrammetrie in der Erschliessungs-
planung und im Waldstrassenbau.
Dissertation, University of Freiburg.