r 
23 
The use of Balplex Plotters in Sweden has decreased during the 
last years due to many reasons. One is that official topogra- 
phic maps in the scale 1:10 000 and 1:50 000 today cover the 
major part of Sweden, giving acceptable topographic informa- 
tion for selection of feasible routes. Another reason is that 
a lot of other factors apart from topography are of great im- 
portance for the selection of feasible routes. 
The major part of public road investments is today allocated 
to by-pass-roads and improvements of the existing road network. 
For by-pass-roads maps are available through city planning of- 
fices and for the design of improvements topographic maps in 
the scale 1:1 000 or 1:2 000 are being produced without any 
prestudy in Balplex Plotter. 
The number of Balplex Plotters disposed by the Road Administra- 
tion has gradually decreased and is today twenty instruments. 
3.5 Map Production 
For the detailed adjustment of the proposed road centre line, 
a topographic map in the scale 1:2 000 is produced using con- 
ventional stereo plotting technique. The maps are supplied with 
a coordinate grid and contours with 1 or 2 metre intervals de- 
pending on the topography. 
At present the following photogrammetric instruments are dispo- 
sed by the Road Administration 
1 Wild AT0 with EkS8 
| Wild A8 with SAAB UE-211 (Swedish-made coordinate printer) 
4 Wild A8 
20 Balplex Plotters. 
The autographs are checked twice a year by grid measurements at 
three different Z-values. During the last ten years the standard 
errors of unit weight for the A8-projectors have varied between 
3,5 - 7,0/m. The corresponding values for the Al0-autograph are 
2,5 - 3,7mm (since 1972). 
For the orientation of the stereomodels, evaluation of test mea- 
surements and model transformations electronic pocket calcula- 
tors (Hewlett-Packard mod 45, 65) and desk calculators (Hewlett- 
Packard mod 9820) are used. 
3.6 Photo Interpretation 
  
In areas with complicated geological formations or bad geotech- 
nical conditions a complete photo interpretation of soil boun- 
daries and characteristics with estimation of soil depths has 
proved to be most useful for the final choice between different 
alternatives in the preliminary design. In addition, such inter- 
pretations make the final design more efficient through a bet- 
ter planning of borings. Finally photo interpretation is useful 
for discovering natural construction materials. 
During the last years the use of photointerpretation has cons- 
tantly increased at the Road Administration. The interpretations