= 1434 -
together with a detailed knowledge of certain parts selected as field checks,
as well as a study of the relevant literature and any pre-existing maps.
Mapping is carried out by interpreting the aerial photographs in an Inter-
pretoscope, a stereoscope with a continous magnification from 20 to 15 times.
The boundaries between the different vegetational units are traced onto trans-
parent plastic overlays, each unit being designated by a code number. The
interpretational work is then followed by a 6-8 weeks field survey for each
5Cokm“ section of the map. Following the results of the field survey, any
necessary changes are made to the transparent overlays. The data contained
on the overlays are then transferred to the topographical base map with the
aid of special device, the Stereo Facet Plotter or Wild B8.
The final map is printed in five colours. The basic colours indicate the
vegetational units, heaths, meadows and mires, which in the majority of cases
also provide a picture of the subdivision of the mountain area into its natural
regions. Colourshades are used to indicate certain ecological factors, viz.
darker shades represent increasing degrees of humidity and/or nutrient status.
The addition of code symbols indicate the mixture of another plant community
within the dominant one, indicated by the colour code, when the former exceeds
30-50% of the plant cover. A series of special symbols are used to designate
such communities as willow thickets, wind-exposed dry heath and boulder-strewn
areas.
The greatest problem which arises in production of the survey vegetation maps
is that of making generalisations. The minimum area of coverage which can be
represented on such a map is ca 300x300 m. Within an area of such an extent
the vegetation may well not be homogeneous, but in fact represent a complex
mosaic of plant communities, many with ill-defined boundaries.
Areas of high species diversity (e.g. rich fen) also pose a great problem for
the cartographer, both when interpreting aerial photographs and when making
the subsequent checks in the field. With few exceptions they are virtually
impossible to pick out on the photos. Field work is very much concentrated to
such species-rich communities for whose presumptive presence a study of the
geological map sheets is invaluable.
The maps are constructed by three photographic interpretors, each of which is
responsible for mapping 5(bakm4 per year. The whole project is thus expected
to need 5 years for its completion and will consist of 20 separate map sheets
and have cost ca 2 million Swedish crowns.
METHODOLOGICAL STUDIES ON THE MAPPING OF SOUTHERN AND CENTRAL
SWEDISH VEGETATION
A vegetational classification scheme suitable for use in the interpretation
of aerial photographs of the plant communities found in southern and central
Sweden has not been specially deviced. Two of the existing classification
schemes have been evaluated in the methodological study and subsequently
modified for use in the interpretation of aerial photographs (fig. 3). The
resultant classification scheme is based on types of natural vegetation cover
present, in conjunction with various ecological and physiognomic factors and
the effects of human influence on the landscape. The scheme is suitable both
for survey maps covering a whole province (scale 1:50,000) and for more de-
tailed maps covering smaller areas (scale 1:20,000, 1:10,000). An assessment
of different kinds of photographic materials has been made, viz. black-and-
FOREST
10 Mixed
11. Conife
133!
12 Decidu
121 |
122 |
123 |
124 |
13 Decidu
131 I
132 |
133-1
134 (
14 Decidu
141 !
142 |
15 Clear-
OPEN FORES
20 Mixed
21 Conife
211!
212 |
22 Warmth
221 (
222 (
23 Other
231 |
232 |
233 |
234 |
SCRUBLAND
31 gunipe
32 Willow
33 Maritir
34 Other
341 |
342
Fig. €
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