signatures. Parametric signatures from objects in feature
space may be drawn from those pixels that fall inside the
object.
A hybrid classification approach was used to utilise these
different class definitions. Within the same process,
maximum likelihood as an parametric rule and feature
space as an non-parametric rule were performed. An
option was chosen: if the number of non-parametric class
definitions in which the pixel lies is O, the pixel will be
submitted to the parametric rule. Among four possible
options in the used software (Kloer 1994), this decision
option provided the best results.
RESULTS
As discussed before, the selected classification scheme
was designed to include all the major land covers
encountered in this area whereby the valleys outside the
proposed park boundaries were excluded prior to
classification.
After the initial classification the accuracy of the new land
cover layer was compared based on random sites inter-
preted on 1:10000 scale orthophotographs. Blocks of 3 x
3 pixels around randomly located points were used as
sample sites. These blocks were stratified according to
class prevalence. The verification was supported partially
by available biotope maps. Therefore, these maps were
digitised and converted to Arc/Info vector format.
Accuracy assessment was performed according to Story
and Congalton (1986). These binomial probabilities are
based on the percent correct and do not account for
errors of commission or omission (Lunetta et al. 1991).
Table 1: Final land cover classes and accuracy
Class Area (km^) | Row. Marg. | Accuracy
1 rock, no vegetation 138 67 9196
2 rock, debis, sparse | 37 24 77%
vegetation
3 meadow 75 48 7196
4 subalpine/alpine pinus | 120 64 8496
mugo societies
5 shrub and bush 26 19 7196
6 water 4.7 7 100%
7 moor 4.1 7 100%
8 subalpine shrub and | 83 35 76%
bush
9 hardwood/conifer mixed | 175 80 70%
10 deciduous trees 45 24 77%
11 pine 37 26 86%
12 pine, young plantation | 35 24 81%
13 coniferous trees 59 35 84%
14 alpine meadow 41 26 88%
15 residential, streets 19 14 68%
overall 500 80,3%
18
An overall accuracy level of 80 percent was attained
(table 1). This level is generally high but it is not fully
satisfying when the availability of existing landcover data
for a third of the area, additional data and hybrid
parametric/non-parametric image classification tech-
niques are taken into account.The combination of GIS
and satellite imagery provides a huge potential not only
within this case study. The GIS allows for the overlaying
of multiple forms of data which makes signature creation
and accuracy assessment much easier.
DISCUSSION
This small study cannot solve the well known problems
of using data derived from photo interpretation for
supervised classification of satellite data. Nevertheless, it
is considerable, that even with very good data availability
and the use of advanced hybrid image classification
techniques, it is obviously difficult to raise the overall
accuracy over 80 percent. Using graphic tools in feature
space layers, non-parametric techniques allow for the
complete" utilisation of the area covered by the
scattergram. In some cases it is difficult to interpret the
corresponding pixels in the image using image alarm
tools and previews. Similar to the integration of super-
vised and unsupervised techniques, it should be possible
to gain from the advantages of two different techniques
rather than to be handicapped by the disadvantages of
both. Commercially available software provided us with
sufficient tools but more research and further
applications are necessary.
REFERENCES
Blaschke, T., 1992, Integration von Satelliten- und GIS-
Daten im geplanten Nationalpark Kalkalpen (Ober-
österreich). Salzburger Materialien 18, pp. 135-148.
Bolstad, P. and Lillesand, T., 1991, Automated GIS
Integration in Landcover Classification. Technical
Papers, ACSM-ASPRS Annual Convention, pp. 23-32.
Ince, F., 1987, Maximum Likelihood Classification,
Optimal or Problematic? A Comparison with the Nearest
Neighbour Classification. Int. Journal of Remote Sensing
8(12), pp. 1829-1838.
Kloer, B., 1994, Hybrid parametric/non-parametric image
classification. Technical Papers, ACSM-ASPRS Annual
Convention, pp. 307-316.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
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