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| COMMISSION IV H1 
| Appendix to the INT. ARCHIVES OF 
PHOTOGRPAMMETRY, Vol. XIk4, 1956 
Methods of Using Aerial Photographs for Mapping | 
  
Purposes in Forests of the State and of Some Big 
Forest Companies in Sweden 
Bulletin from the Committee of Forest Photogrammetry 
By Nils Hagberg 
Survey of forest resources and needs for mapping 
Sweden counts as one of the most characteristic woodland countries of 
the world. About half of the country's exports are made up of forest pro- 
ducts. More than half of the country's area is covered by forests. Disregard- 
ing the area of ten thousands of lakes, swamps and other improductive land 
scattered in the forest regions, the use of productive forest land comprises 
nearly 230 000 sq. kilometres (57 million acres). Roughly speaking, half 
of this area belongs to farmers and lacks forest maps. The rest, which is 
owned in equal parts by forest industries and the Public, is for the most 
part mapped. Forest maps are usually revised at intervals of 10—20 years. 
Consequently, the area to be mapped annually is somewhere around 5 000 
to 10000 square kilometres (1— 2.5 million acres). Difficulty has been 
experienced in getting the vast and expensive mapping projects carried out 
in time. Aerial photos have therefore been used since 1930, and since 1948 
to an ever increasing extent, with the big forest enterprises leading in this 
field. The area mapped with the application of methods based on aerial 
photography is increasing rapidly and at present represents something 
around 20 000—30 000 sq. kilometres. 
Natural conditions and forest administration 
The new mapping methods arrived at differ greatly from each other. 
One substantial reason for this is to be found in the divergent forms of the 
natural features. The length of the country, measured from south to north, 
is 1 600 km (about 1 000 miles). In the southern parts of the country with 
prevailing natural conditions much resembling Central European con- 
ditions, the average annual volume increment of forest stands can be 10 
15 cubic metres per hectare and the average height of mature stands 25-—30 
metres. In the northern parts of the country, mainly located north of the 
Arctic Circle, the average volume increment for extensive forest areas is 
not more than 1 cub. metre per hectare, and the average height of mature 
stands is about 10 metres. There is no forest cover in the northern region 
at altitudes exceeding 600 metres above sea level. On the other hand, there 
is less divergence in the topography of the country, as even in the north 
the forests are mostly located in moderately hilly regions. Forest stands 
often lack definite boundaries. In Southern Sweden they run to a size of 
some 1— 3 hectares, while in the north their size is often more than ten 
times as much. 
A forest district is managed by a district forester, often with the help of 
an assistant forester, and 3—10 rangers. The area of a district in the south 
is 50—200 sq. kilometres and in the north 500—2 000 sq. kilometres. As a 
rule a district is divided into a number of blocks, often more than a