GVII-8 (Sup,) 
ENGINEERING APPLICATIONS 
Hydroelectric Power Applications 
In Sweden during the last ten years, the Swedish State 
Power Board has ordered aerial photography (specially made) 
for all rivers and probable reservoir lakes in northern 
Sweden, which has not yet been taken into the hydroelectric 
system. These aerial photographs have been used for photo 
interpretation and for mapping. Initially, the photo inter 
pretation was mostly rather simple, but since about one year 
ago, more advanced studies of the pictures have been carried 
out to get information about the soils, vegetation, etc. 
This photo interpretation is carried through with the Old 
Delft stereoscope, two of which we use together when dis 
cussing our problems with the geologists© The methods are 
still under development. 
A special trial is now being made in Sweden to determine 
the possibilities of making the planning of high-voltage 
power transmission lines more efficient through the use of 
photo interpretation and photogrammetry. The method is as 
follows: 
1, Through a simple mechanical radial triangulation 
(lazy-daisy) we determine the horizontal position of about 
nine points in every photograph in the scale Is 20,000 for 
the test area (100 km long and 6-12 km wide). The limits 
of this area have been determined through a careful inves 
tigation with the aid of existing small-scaled topographic 
maps, etc., in order to find where there are no prohibitive 
obstacles for a line. 
2. With a sketch-master, or in some cases by tracing 
directly from photographs onto the translucent base sheets, 
roads, lakes and villages are transferred to the simple 
radial-plot base sheet. These maps are intended for 
summing up of the interpretation results. 
3© The area intended for interpretation is marked 
on every other picture, in order to avoid duplication and 
reduce the interpretation work to about 50$ through ex 
cluding of the overlapping part of the stereomodels. At 
the same time, such areas close to lakes, etc., are 
marked where from a geometrical point of view it is im 
possible to place the line. Thereafter soil interpreta 
tion is carried through in order to divide the groundinto 
basic soil types (moraine, rocks, sandy areas, marshlands, 
etc.). 
ii. On every other photo a grid 15 x 50 mm oriented 
along the main direction of the power line is drawn.