20, 
The DTM will form the basis on which optimization procedures in 
Highway Design will be based. In England the official DTM-system 
is based upon a variable square grid, but in order to improve 
the data collection a new system for the DTM is under develop- 
ment and introduction - the String DTM. Essentially the String 
DTM consists of a series of strings of coordinates. There are 
basically two forms of strings - 
Il 
Contour 2-dimensional string 
Break Line 3-dimensional string 
Using this concept of design the Highway itself will be treated 
as a series of strings, i.e. channels, verges etc will each be 
an individual string. This will form a separate DTM. The interac- 
tion of the two DTM, Hichway Design and ground surface, will then 
enable volumes and slope-stake intersections to be computed without 
recourse to the traditional cross-section. (Further information 
concerning the optimization and the British DTM can be received 
from the Road Research Laboratory, Crowthorne, Berkshire, England). 
In Czeckoslovakia a system of DTM was developed in 1969 and veri- 
  
fied on the Czeckoslovakian test field Pecn$ and in 10 km section 
of motorway in open terrain. Nevertheless the system has not been 
introduced in practice yet due to shortage of a suitable computer 
with a large operational memory. In 1972 the program will be trans- 
ferred to an IBM 360/40 computer. 
In Czeckoslovakia, owing to a sufficient amount of topographic 
maps, application of the DTM is suggested for the following tasks 
only. 
A. Final Design of complicated Interchanges and Intersections. 
B. Choice of alternatives in rough open terrain, (sections of 
some Kilometers only). 
The system developed at the Research Institute of Geodesy 
and Cartography will be incorporated into a large system of 
data processing as follows: 
«9 
(€ 9