ORGANIZATION OF THE WORK. 
The question concerning a practical air photo scale for Swedish 
forestry was taken up as one of the first points of the program 
when the Committee started its work in 1955. With the kind 
assistance from the Geographical Survey Office the following 
two test fields have been photographed: 
Ostad in Västergôtland and 
V. Skedvi socken in Västmanland. 
Flying altitudes: 2 500, 3 900 and 5000 metres (8 000, 13 000 
and 16 000 feet). 
Camera: Wild RC 5 a. Focal length 15 em (6^). 
Size of negative: 23X23 em (97). 
Moreover, photographs taken in 1954 with the same camera 
from two different altitudes, 3 900 and 5 000 metres (13 000 and 
16 000 feet) over a test field in Hällnäs, Västerbotten, have been 
used for the investigations. 
As the purpose is to compare different photograph scales, il 
is important that the taking of the pictures from the different 
altitudes is accomplished under consistent conditions, if possible 
simultaneously, so that differences in weather conditions and 
other factors will not cause differences in quality of the pictures. 
This has been taken into consideration as much as possible. 
However, the photography from one of the altitudes had to be 
repeated, causing displacements in time amounting to a month. 
To get an idea of the differences in picture quality which might 
exist, the negatives were graduated according to a 5 grade scale 
by ocular estimation. There were no marked differences in pic- 
ture quality. 
Data of the photographs is given in table 1. 
To get an idea of the use of different photo scales from the 
point of view of forestry it is necessary to know how aerial 
photos are utilized in forestry. Three different fields of ap- 
lication can be distinouished : 
D 
1. The photographs used for maps. 
2. The photographs used for measurements. 
3. The photographs used for interpretation (for planning ete.).