- 1436 - 
ng färgfilm 1:20 000 Antal Rätt tolkat 
Interpretation IR-colourfilm 1:20 observ. 
Fältbestämning 95% konf. 
Ground truth 0 [11 [12 | 13j14 |15 j21 | 22 1 |32 |34 | 41 3 |44 observ. interval 
  
Fig. 4 The accuracy in the classification 
measured by comparing interpretational and fieldwork. 
IR colour film at scales of either 1:50,000 or 1:20,000, a somewhat better 
agreement was obtained between the vegetational boundaries distinguished on 
the aerial photographs and those actually found in the field. A greater degree 
of details was possible, and the classifications were found to be correct in 
80-90% of all cases (fig. 4). 
The inherent weaknesses connected with the interpretation of aerial photographs 
are the specific identification of different trees and the poor possibility of 
assessing the nature of the field layer in forested areas. The latter require- 
ment is particularly important for maps on a scale of 1:20,000. Making vegetation 
maps from aerial photographs therefore by no means obviates the need to carry 
out field surveys. The advantages of making vegetation maps from IR colour film, 
compared with the conventional methods of field surveys in conjunction with 
panchromatic photos as a basic aid, are that none detailed maps are obtained, 
on which the vegetational boundaries are reliable, as well as the vegetational Fig. 5 
classification, and the amount of time involved is much reduced (5-10 km2/hour 
for a survey map on a scale of 1:50,000). For more detailed maps (scale 
1:20,000) a mapping speed of 1-2 km per hour is practicable, compared with 
only 1-2 km? per day by conventional fieldbased mapping Fig.5 
PRACTICAL APPLICATIONS Refer 
Aerial photography using IR colour film is an expensive business, because you Borg, 
have to order special photography. Therefore, it has not been used to cover fy 
any particurlarly large areas of the country. Plans are in preparation for Ihse,M, 
producing a vegetation map for the province of Norrbotten, using IR colour ve 
film and the methods described above (scale 1:50,000). The map will be used En 
in conjunction with a survey of reindeer grazings and for nature conservation Ihse,M, 
ce 
purposes. Interpretational keys are being prepared for use in training-up a 
start of aerial photograph interpretors for this project Swe