18 
These experiments are described in Öst. Zeitschr. f.V.W., XXXVI. Jhg.-v. Dez. 1948. 
To this account is also added the detailed plotting of two districts, Fluh and Buch in 
Vorarlberg, which was made from aerial photographs on a picture scale of 1:8.000 for 
a plotting scale of 1:10.000. Explanatory data are given in the paper »Das Luftbild als 
forstwirtschaftliche Erkenntnisquelle», (Technik u. Wirtschaft, Sept. 1947, No. 23/24, p. 
5—7) and a paper »Die Holzmassenermittlung nach Luftbildern» (Allgemeine Forst- und 
Holzwirtschaftliche Zeitung, No. 13/14 and 15/16, July and August 1948). These data 
correspond to the answers to the questions 1—8, 11 and 12 of the questionnaire. 
As a result of these investigations a picture scale of 1 : 5.000 is required 
for a plotting accuracy of 1,25 m for diameter of tree-crown, 60 cm for 
tree-height and 8 cm for diameter breast-height to obtain a satisfactory 
determination of volume. When comparing a ground survey of 1935 with 
an aerial survey of 1939 of the forestry district Schottenhof near Neu- 
waldegg, a difference of 6 per cent was established but it must be con- 
sidered that the picture scale of 1: 10.800 which was used is too small for 
such investigations. 
The relation between the different words in the terminology of the 
science of production must also be investigated, e.g. brest-height diameter 
— crown-diameter, crown-height — tree-height, crown-breadth — crown- 
length, stem-number — tree-height — stand-volume; further, volume- and 
yield-tables must be worked out. 
Finland: 
(a) Air photographs are mostly used in forestry for determination of site 
for estimation purposes. Practically all determination of site is made on 
photographs nowadays. In 5 years the area determined will be about 
80.000 km?. 
Aerial photographs are also used in forestry mapping. Through the Board 
of Forestry 270.000 hectares have been mapped, and preliminary base 
measurements have been made in an area of about the same size. It must 
be mentioned that in forestry mapping, based on aerial photographs, an 
ocular estimation of the stand is also made. By using photographs, the 
speed and accuracy of the estimation is considerably increased. Industries, 
private enterprises and forestry committees have undertaken smaller map- 
ping projects. 
(b) In the site determination work photo-maps, scale 1 : 4000 or 1 : 8000, 
are used, or square or rectangular parts of aerial pictures, which are recti- 
fied, and enlarged to the scales mentioned above. The aerial picture sheets 
usually form a coherent map of a large area, usually a district. In the 
determination of site only single pictures are used. 
In regular forest surveying at the Board of Forestry, rectified pictures, 
taken with wideangle lenses, scale 1: 40.000, and enlarged to the scale of 
1:20.000 were used. These pictures were used for mapping in Lapland. 
In an experimental surveying of 1.000 hectares in the south of F inland 
photographs were used, taken with a normal-angle camera on a scale of 
1: 20.000 and enlarged and rectified on a scale of 1: 10.000. The pictures 
were used as stereoscopic pictures, as stated below, and were studied in 
a stereoscope or through stereoscopic glasses, 
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