€ discernible,
'egetation are
zation
rsion
re 3d) linear
ing serves as
wes and the
t which the
intensity changes sharply, giving in this way picture of the
boundaries.
Figure 3d. Gallikos river, Sobel operator
Axios (figure 2, number 4) is an important interboundary river
in northern Greece. Its estuaries in Thermaikos Gulf, form a
large bird-foot delta (as defined by Zuidam et al, 1979) (figure
4).
Figure 4. Axios delta
The area has been formed by a combination of fluvial processes
with marine influences. Several fluvial features (as tributaries)
as well low vegetation (tonal and textural differences) in the
riverbed can be discerned in figure 4. Cultivated areas on the
left and right side of the riverbed and linear forms of roads are
also detectable. The river transports and deposits material at the
estuaries, detectable from the changes of light to dark tones in
the mouth of the river (Lillesand T.M, 1987).
The application of point operations (figures 4a, 4b) substantially
helps to the detection of the above. The areas of deposition in
the sea have characteristic form.
Figure 4a. Axios delta — histogram equalization
Figure 4b. Axios delta — brightness inversion
The application of local operations (figures 4c, 4d) enhances
details as areas of low vegetation, cultivations, roads, riverbed
boundaries and highlights the changes in image intensity
detecting boundaries of similar regions.