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hand the Swedish triangulaticn net is relatively sparse. Forest stands are 
mostly of even aged type. Especially in Northern Sweden (Norrland) they 
are somewhat sparse. They rarely reach an average height cf more than 
20—95 meters. Because the sun in these latitudes never rises very high 
the shadow is long, and this often makes it more difficult to study the 
photographs. The main trees in the forests are Scotch pine and Norway 
spruce, often mixed stemwise in the stands. There is also speradic birch. 
Forest fires, windfalls, snowbreaks, and insect injuries are rather com- 
mon but rarely lead to damage of catastrophic proportions. 
Sweden is one of the countries in the world that is most markedly a 
land of forests, and silviculture receives a great deal cf attention. Manage- 
ment plans and forest maps, usually on a scale of 1:10.000 (in Northern 
Sweden 1:20.000), are drawn up every 10—15 years for all important 
forests. As early as in the nineteen-twenties the first attempts were made 
to use aerial photographs in forestry. In the years 1930—1932 the represen- 
tatives of forestry in collaboration with other interested parties arran- 
ged considerable experimental phetographings in different places in 
the south of Sweden. First an attempt was made to find out how to use 
the aerial photographs for different kinds of cartography. Experiments were 
made both indoors and on the ground and some instruments were also 
tested. Further, economic and organizational problems involved in aerial 
survey of large areas were studied. The most important result was that, 
when making economic maps in Sweden, only photogrammetrical methods 
are now used. The aerial photographs were used for forest cartography 
also, though from the start only to a small extent and after rather un- 
developed methods. 
During the nineteen-forties there was a considerable labour shortage in 
forestry and this made it impossible to carry out cartography and estima- 
tion of volumes as planned. Especially in crown forests and those of the 
great forest companies aerial photographs came in use more and more to 
supply the need for new maps. And this made clear the defectiveness of 
the methods used in photogrammetrical cartography. The question arose 
whether aerial photographs could not be used for estimation, planning of 
ditching, roadbuilding etc. Experiences from other countries had cer- 
tainly been studied but practical tests had shown that they seldom were 
directly applicable to Swedish forestry. This gradually led to an increasing 
demand for regulated Swedish research into a suitable way of using aerial 
photographs within Swedish forestry. At the same time it was difficult for 
the Geographical Survey Office, which attends to civil aerial photography 
in Sweden, to satisfy the rapidly growing demand for aerial photographs 
and their revision within reasonable time, and at costs that were not too 
high. Claims have been made for a reorganization cf the cartographical 
institutions of Sweden. The Committee on Forestry Photcgrammetry has 
been appointed to throw light on matters of research and organization. 
Since the research question was becoming urgent the committee itself has 
begun many experiments in collaboration with technicians as well as re- 
presentatives from practical forestry. 
ERIS 
2 
EAT 
pidum