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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
Ground resolution of IKONOS data is smaller than the average
patch sizes of the vegetation classes of this study, and pixel
values alone may not provide enough information for
distinguishing image objects corresponding to the instances of
vegetation classes, although pixel-based classifiers such as
maximum-likelihood classifiers provide useful vegetation
information such as vegetation density and distribution in
individual patches of vegetation classes. On the other hand,
object-based classifiers can utilize contextual information as
well as spectral information for image classification, and are
suitable for delineating image objects corresponding to the
vegetation patches on IKONOS imagery. They group
contiguous pixels with similar pixel values into image objects
and label them according to contextual information such as
spatial relationships among image objects as well as spectral
and textural properties.
3. STUDY AREA AND DATA
In this study, a trial of the hybrid vegetation mapping
from actual IKONOS data was conducted. The lower part
of the Nivodo river watershed area located in the south-
western part of Japan was chosen for the study area. The
land use of the study area mainly consists of natural
forests and agricultural fields (rice fields, vegetable fields,
green houses, etc.).
The remote sensing data used in this study is the IKONOS pan-
sharpen CIR imagery data produced from the panchromatic and
multi-spectral IKONOS data taken on November 21, 2001 for
the study area.
4. IMAGE SEGMENTATION
Object-based classification starts with the image segmentation
process, which delineate image objects with relatively similar
properties according to segmentation criteria. In this study, the
segmentation algorithm developed by Baatz and Schäpe (2000),
implemented in the e-cognition* * software, was used to
conduct image segmentation of the IKONOS data with multiple
scale parameters to see the correspondence between image
objects and land cover instances including vegetation patches.
The calculation parameters of the multi-scale segmentation used
in the segmentation were "colour" (weight 0.8), "shape"
(weight 0.2, further, the “shape” parameter consists of
“smoothness” (weight 0.9) and “compactness” (weight 0.1)).
Figure 1 shows some examples of the segmentation results at
different scale parameters. These are at some intermediate steps
of a region growing process from individual pixels. Figure 1 (b)
Figure 1. Segmentation results with different scale parameters
(a) IKONOS (* 3SI) image, (b) Scale parameter 20, (c) Scale parameter 80, (d) scale parameter 300
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