Finland 
been used in timber inventory, mapping, management, planning work, and in administra 
tion. I hese photographs cover an total area of about 6 ooo km 2 . 
Special investigations. A study on the estimation of the growing stock from 
aerial photographs has been published in 1955. 1 The study is divided into two major parts. 
The first part is based upon stand material measured on ground. The mean height, crown 
closure, and crown diameter are studied as growing stock characteristics. 
Measurements from aerial photographs make up the second part. The photographic scale 
of the material is in South Finland 1 : 10000 and in North Finland 1 : 15000. Both pan 
chromatic and infrared material are used. The height measurements are carried out using 
parallax and shadow methods. Standard mean error of the estimate fluctuated from 0.9 to 
2.9 m. The crown closure is measured by dot grids and density scales and the standard error 
of the measurements fluctuated from g to 16 per cent. The diameter of the dominant crown 
is measured by measuring wedge, micrometers, and diameter scales, the standard error of 
the estimate fluctuating from 0.58 to 1.6 m. The systematic error was rather high and after 
excluding it the limits for standard error are 0.42 and 0.66 m. 
The standard error of estimate for the growing stock volume was approximately 30 per 
cent and for mean diameter 15 per cent. 
Lake regulation and water power planning. 
During the period 1952— 1955 photogramme try has become established in use for mapping 
in connection with planning of lake regulations and water power plants. Besides that the 
pictures as such have been employded in many preliminary investigations, single pictures and 
stereo photogramme try have been side by side used in these mappings. 
Single picture photogrammetry has been especially used in shore investigations of lake 
reservoirs. Partial enlargements from normal-angle pictures 1 : 20 000 were rectified into 
1 : 4 000 so that the area to be mapped is covered with photo sheets. Using these sheets, 
0.25 m contours were leveled in the terrain between the upper and the lower water level 
in the reservoir. This strip comprises only a few metres in the vertical direction. The field 
investigation has also been made on these sheets in connection with the levelling. The sheets 
thus obtained are also used as a basis for maps required by appraisal of agricultural and 
other losses. The relief displacement has no important effect because of the flatness and 
narrowness of the shore area to be investigated. 
These methods have given good results on the populated lakeside areas of South-Finland, 
where the regulation height is relatively low and a high contour accuracy is needed requi 
ring a small contour interval (0.25 m). 
Since about 1952 the focus of the reservoir and power plant planning has moved into the 
sparsely populated North-Finland, where high regulation levels are necessary. For this 
reason stereophotogrammetry has become more and more predominant, displacing single 
picture methods almost entirely in 1955. 
During 1952—1954 the most part of the river Kemijoki has been mapped at the scale of 
1 : 4 000 with one meter contours. The aerial photography 1 : 20 000 was made with a Zeiss 
wide-angle camera RMK 10/18 X 18, flying altitude 2 000 m. The extension of the horizontal 
control and plotting of the map were accomplished with Zeiss stereoplanigraphs. Vertical 
control was established by leveling. The total area mapped in this way covers 426 km 2 . 
In 1955 the power companies of the Government have established their own photogram- 
metric bureau, and purchased two autographs, Wild A 8 and A 7, accompanied by a Wild 
camera RC 5 a. During 1955 a total of 2 155 hours was used for the mapping work, which 
consisted of 282 km 2 maps in 1 : 4 000— 1:10 000, photographed with a wide-angle camera 
1 N y y s s 6 n e n, A a r n e: On the estimation of the growing stock from aerial photographs. 
Comm. Inst. Forest. Fenniae 46.1 Helsinki 1955. 
See also: Ilvessalo, Yrjo: On the correlation between the crown diameter and the stem of 
trees. Ibid. 38.2, Helsinki, 1950.