»
negative effects of the traffic is growing tremendously and the
decision process becomes more delicate from year to year.
It is therefore important for the engineer to have an easy access
to all required data or information in an acceptable form and to
aids for processing the data in different ways for investigation
of alternative solutions. He must also effectively be able to
investigate the consequences from different aspects of the alter-
natives and he must finally be able to present his result in a
form that can be understood and accepted by all the different
people that today are involved in the process of decision. The
environmental consequences become more and more important for
the people and on the same time the opposition towards proposals
without an acceptable description of positive and negative conse-
quences from many different aspects grows. In other words the de-
mands for an improved technique for the highway and railway plan-
ning and design are today stronger than they were in 1960 despite
the fact that the volume of road and railway construction in many
countries has decreased.
The development of the sciences around photogrammetry as surveying,
electronic data processing and automatic plotting has been very
effective since 1960 and the conditions for improving the system
of aids for planning and design are today better than ever. The
possibilities to play over a wider register are great.
Digital terrain Model
The attempts to automatize the design process have been active du-
ring the recent ten years. The introduction of the Digital Terrain
Model, DTM, technique seemed from the beginning to be very promi-
sing. An effective way of acquiring and storing topographic and
geologic information was found. The further experiences of the use
of the DTM-technique has, however, so far not come up to the expec-
tations. Many different designs of DTM with different systems for
the interpolations of the surfaces have been developed and intro- A
duced. The DTM-technique has so far mostly been applied for the
calculation of earth quantities, cut and fill. The earth quanti-
ties do play an important role in the modern design, but there are
other parameters, road safety, environmental and aesthetic conse-
quences etc that in the final decisions also receive a heavy weight.
The DTM seems therefore so far to be of a greater importance as an
aid for the design of road intersection and interchanges and for
planning and design of residential and industrial areas. In these
cases it is generally a question of acquiring topographical and
geological data over limited areas. The highway planning and de-
sign, however, require information over long and narrow corri-
dors. A similar statement was made already in the report of the
Working Group to the ISP congress in 1972.
A very interesting progress concerning the development and applica-
tion of the DTM-system is reported from England, where the develop-
ment and introduction of different digital models has been inten-
sive during several years. The initial models stored ground levels
at the intersection of a superimposed square grid and although it >
was a convenient computer solution for storing a three dimensional
mode | it was not always satisfactory because it did not allow suf-
ficient definition of irregular terrain and features such as roads
and railways. Several attempts have been made to improve ground mo-
dels such as defining the ground by random points or a series of
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