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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXX V, Part B7. Istanbul 2004
index. The correlation matrix between the bands of MS image
and the fused image are presented in Table 1. This matrix
indicates the correlation between the bands of each image and
the correlation of the corresponding bands of the two images as
well. Thus the spectral quality of the fused image can be
evaluated.
MS image Fused image
B. 1 B2]5p.35|!p41]BJ] B.2 | B.3 | B4
B. I 0.98 | 0.93 | 0.17 | 0.92 | 0.87 | 083 | 009
B.2 | 0.98 ] 0.97 | 0.25 | 093 | t.9t | 090 [ 0 17
B.3 | 093 | 0.07 | 0.17 | 0.88 | 0.88 | 0.92 | 0.10
B.4 | 0.17 |.025.] 0.17 | 0.39 | 0.48 | 041 | 0.96
B.1 | 092 } 0.03 ! 088 | 0.39 1 0.98 | 0.93 | 0.36
B.2 | 0.87 | 0.91 | 0.88 | 0.48 | 0.98 ] 0.97 | 0.45
B.3 | 0.83 | 0.90 | 0.92 | 0.41 | 0.93 | 0.97 ] 0.38
B.4 | 009 | 0.17 | 0.10 | 096 | 036 | 045 0.38 1
Table 1. Correlation matrix between the bands (B) of MS image
and fused image
The application of the NDVI index and the computation of the
correlation matrix between the two NDVI images, gave the
value of coefficient correlation 0.95.
Thus, safely we can conclude that the fused image preserve the
spectral characteristics of the MS image (Tsakiri et al, 2002).
The assessment of the spatial accuracy of the fused image has
been occurred via the registration of the new image into ortho
Pan. This procedure has been done with an accuracy of
RMS=0.4m. In Figure 3 an extract of the fused image is shown.
Fig. 3. An extract of the fused image
3.2 Interpretation
As is already mentioned, the interest of this study is focused on
some traces that already have been identified on the
orthomosaic. These features concern parts of Via Egnatia, a part
of a defensive wall and the buried construction on the top of a
hill.
The initial visual interpretation of the PAN and MS images
gave a quasi total different appearance of the traces. The
features were more intense. Additionally, while in the
orthomosaic the traces have been appeared with discontinuities,
in the PAN image much more parts of the features have been
located. This was valid for the fortification wall (Fig. 4, 5) and
Via Egnatia (Fig. 8, 9). Totally different was the appearance of
the buried construction (Fig. 10, 1 13.
In a second step the interpretation of the fused image has been
done. The empirical method of combination of bands for color
display was applied. Certainly, there is no single ideal
combination. Likewise, many factors affect the result for the
archaeological interpretation. In the Figure 6 the image of the
fortification wall is presented, as result of the combination:
R=1, G=2, B=4.
To facilitate the trace’s identification and interpretation, the
PCA transformation was applied on fused image. The three
selected PC1, FMSI and PC2 bands have been enhanced by
applying the convolution filter 3x3 for edge enhancement.
Finally a FCC image was produced by displaying respectively:
R-PCI, G-FMSI and B=PC2. In Figure 7, the image FCC of
the fortification wall is presented. Via the interpretation of this
display some additional details of the wall have been identified.
4. CONCLUSIONS
The aim of this project was the evaluation of the possibilities
that the high resolution satellite image Quickbird-2 contributes
to the detection of buried archaeological remains. The research
is still in progress. Our interest is focused only on the features
that have been already identified on the aerial photos. The first
results are promising.
The initial visual interpretation of the PAN and MS images
gave a clear and intense appearance of the traces. Additionally,
while in the orthomosaic the traces have been appeared with
discontinuities, in the Q.B. images much more parts of the
features have been identified. It is already noticed that the data,
orthoimage and Q. B. images, was captured in different season.
Thus the question is: season is the only parameter that affects
the result?
Additionally, a preliminary application of image processing
techniques on the fused image, revealed some additional details
in the trace of the fortification wall. In this direction much more
efforts will follow in the future. Others digital image analysis
will be applied.
Ground truth reconnaissance about land use and land cover will
be realized next month, May 2004. As Q.B. images were
captured in May 2002, this work will help the research. Ground
truth reconnaissance will be repeated in September, the same
time aerial image has been taken.
The spatial ground resolution of Q.B. images allows: A) the
identification of a large range of archaeological features. Till
now, our interest is focused only on the features of Via Egnatia,
the defensive wall and a buried construction. As is already
noticed, a hundred of traces appear in the orthoimage. Thus, the
study and interpretation of the fused image for the identification
of other archacological traces will be done. B) the accurate
surveying of the archaeological site. As the fused image is an
orthorectified satellite image, all necessary information for the
documentation of the archaeological site and the identified
traces, is already here.
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