International Archives of the Photo
The characteristics of the new digital remote sensed image, like
IKONOS-2 become these data a valuable source of
archaeological information (Campana, 2003). Today, the
panchromatic (0.7m spatial resolution) and the multispectral
(2.5m spatial resolution) images, offered by the satellite
Quickbird-2, enable users to dispose and manipulate data of a
large archaeological area, in a large portion of the optical
spectrum, with a high spatial and radiometric resolution. In
addition, the application of rigorous digital image analysis
techniques in these data, can give valuable information to the
archaeologists.
The aim of this project is to evaluate the possibilities that the
high resolution satellite image Quickbird-2 offers for 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 and the
orthomosaic, that means Via Egnatia, the defensive wall and the
buried construction on the top of a hill, called today the hill of
Alexander the Great.
2. STUDY AREA AND DATA SET
2.4 Study area
The site of study is the major area of the archaeological site of
Philippoi in N. Greece (Fig. 1)
pe t
LAAT AREA hag ATHENS 3 AM o
Fig. 1
It is a countryside landscape, with fields, villages and low
height relief. The archaeological site of Philippoi, where the
excavations are taken place, and the major area of it, where our
attention is focused, are presented in Figure 2.
2.2 Data set and Pre-Processing
For this research a data set of Quick Bird (Q. B) satellite were
used: a panchromatic image and a multispectral one. The Q.B.
images were acquired in the 23th of May 2003. This time of
capture offers two advantages: the images are recent and, in the
grammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. isidtibui 2004
same time, near the year of the aerial images. Thus, no many
transformations and changes in the area have been occurred in
the period of 8 years. Secondly, in May the conditions for the
detection of archaeological features are good. It is noticed that
the aerial photos were captured in September. Thus, data of two
different seasons were available. The Q. B. images were
characterized by very good quality. The total absence of cloud
and haze offered an excellent visibility. They covered an area of
8.5Km x 8.5Km.
- : 43 4 M
Y .
asd ,
A. Archaeological site
B. Area of study
The spatial ground resolution of 0.7m (PAN image) is
approximately twice the resolution of the aerial photos already
processed. The trace of Via Egnatia is of 6m width. That means
that the spatial resolution of 0.7m of Quickbird-2 PAN image is
adequate to distinguish the same trace. On the other hand the
MS image has a spatial resolution of 2.5m but includes
information that neither the aerial image nor the PAN image
has. A fused image is characterized as the PAN image in four
bands. Thus a new image, the fused, was necessary to be
produced.
[n order to proceed in generation of a fused image, the
orthorectification of the Q.B images has been preceded. A DTM
produced from aerial photos was available. Additionally six (6)
Ground Control Points (GCPs) measured by GPS were
available as well. The images were orthorectified with the aid
of Leica Photogrammetry Suite software. The procedure was
based the Quickbird sensor model. The orthorectification of
PAN and MS images has been done with accuracy (RMS) of
0.66pixels and 0.5pixels respectively. Before the fusion process
the ortho MS was registered to ortho PAN in order to fit better.
3. DATA FUSION AND INTERPRETATION
3.1 Data Fusion
In order to fuse the Panchromatic and Multispectral images, the
PCA transformation was used. The spectral quality of fused
image was evaluated by the correlation matrix and the NDVI
1056
Int
ind
anc
ind
the
we
eva
32 I
AS is ;
some
orthon
ofad
hill.
The ir
gave i
feature
orthoir
