FINLAND 7 
The Board of Forestry is carrying out quite extensive forest mappings in the 
large state forests in North-Finland. The mapping method is about the same as 
explained in the Report of 1956. Essential to this method is that the sparse geodetic 
control net is extended by using radial-plotting. Photographs which have been 
rectified by using the horizon angles are used in this radial-plotting, which is carried 
out with spider templets. Some experiments have also been made with the Zeiss 
Radialsecator I. 
The stereoscopic photograph interpretation has been found out to be correct 
in 80—90 cases of hundred, in spite of the small scale of the photographs, in the 
distinct forest areas of North-Finland. The forests in South-Finland are much more 
difficult to interpret, therefore the use of aerial photographs is limited there to some 
few single objects. 
The inventorying work is counted to have been speeded up about 20—40 % 
in South-Finland and 50 % in North-Finland compared with the earlier field 
methods. 
Lake regulation and water power planning 
The state-owned power companies set up in 1955 a mutual photogrammetric 
service which carries out mapping with autographs in scales 1 : 500—1 : 10 000. 
The waterfalls which have not yet been built up are situated in North-Finland, 
and so the works of the service are also concentrated therein. The coarse network 
of highways and the sparse geodetic control in this area set their own obstacles to 
the work of the service. Helicopters are much used to speed up the geodetic surveys. 
Tellurometer has been used for measuring distances and experiments have been 
made also with a Geodimeter. 
The aerial photography is carried out with Aviogon and Pleogon cameras. 
Aerial triangulation has been carried out with autograph A7 in scales 1 : 10 000 
— 1: 30 000 on an area of about 18 500 km? during the years 1956—1959. Merely 
in 1959 about 7000 km? were triangulated. 
An area of about 13 200 km? has been mapped with A7 and A8 instruments 
during the same period. The most part of this has been made in scale 1 : 10 000 with 
2.5 and 5 metres contour interval, and the rest in scales 1 : 500—1 : 4000 with 
0.5—2 metres contour interval. 
The shore investigations of natural lakes are carried out by using also the single 
photograph measuring. The photographs are taken in scale 1:30 000 and the 
control extension is made with aerial triangulation. The photographs are rectified 
and enlarged with the aid of the instrument values, after which the 0.25 m contours 
are surveyed in the flat shore areas on these enlargements by using the field survey 
methods. 
Other uses of aerial photographs 
In the classification of land for taxation on rural areas, rectified enlargements in 
1 : 4000 of aerial photographs are still used as a base map. This work is carried out 
in the same way as described in the Report of 1956. However, this work is now 
diminishing because most of the communities are already mapped for this purpose. 
During the years 1956—1959 photographs were prepared for this purpose covering 
an area of about 47 000 km?. Until this the classification has been carried out in 
410 communities, covering a total area of about 253 000 km?, which is about 83 % 
of the whole country. 
Checkings of these classification surveys have been made in the Photogrammetric 
Division of the General Survey Office both with autograph and with radial-plotting 
method,’ covering an area of about 100 km? annually.