Jökull - 31.12.2001, Side 8

Jukka Káyhkö et al.
Figure 2. A thick aeolian deposit near Nýjahraun, along the road no. 1. The dunes in the region show abundant
erosion scars suggesting that some alterations in the wind-sediment supply and vegetation system are taking
place at present. - Rofabarð nálœgt Nýjahrauni, S-Þingeyjarsýslu. Mikil jarðvegseyðing hefur átt sér stað á
þessu svœði.
formed unsupervised Isodata classification using the
Erdas Imagine® version 8.4 software package. The
classification parameters were determined as a maxi-
mum of 30 statistical clusters with a 5 percent change
limit between iterations.
We visited 91 field plots and described them with
regard to their lava/sedimentary cover and vegetation
(where applicable). GPS was used for navigation to
all plots. The statistical clusters were assigned with
respective field plot descriptions, thereby resulting in
land cover classes. Comparison of the classification
with ground data demonstrated that, at the radiomet-
ric and spatial resolutions used here, relatively dis-
similar lava and sediment surfaces can show com-
parable reflectance patterns. After thorough signa-
ture investigation, some classes with relatively simi-
lar ground features were combined (visually) by as-
signing these classes the same colour on the map. A
nomenclature based on the land surface characteris-
tics was built, resulting in 19 classes within three cate-
gories. The classified image was rectified and georef-
erenced (WGS84/UTM28) based on ground control
points measured on 1:50000 topographic maps, and
additional GPS points.
RESULTS
The 19 land cover classes generated by our man-
ual inspection of the unsupervised classification result
were combined into three land surface categories (Fig-
ure 3):
a) Lava cover; 31.6% of the area with six classes.
b) Barren sediment cover; 45.4% of the area with
two erosional and seven depositional surface
types.
c) Miscellaneous (including vegetation); 23.0% of
the area with four land cover classes.
6 JÖKULLNo. 51