e public, through a
interpretation and
of their own city.
ol of all changes to
formed" decision-
the use of current
1 and Information
ting efforts of the
) while similar
iques have been
.ousoulakou et. al.,
ok et. al, 1996,
jerra et. al., 1999,
el Din et al., 1999,
STORY
y in Greece, has a
traces of the first
le city is founded
rs by Kassandros,
:xander the Great.
it historic periods,
an and finally its
epeatedly suffered
ls, Arabs, Francs,
thy Thessaloniki,
velpoped public
and an electric
e part of the inner
to many wooden
was on for three
ff the damage is
me (see Fig. 1)
ban plan has been
to which the city
of course been
ve been salvaged,
architectural and
al value, the city
de drawings, old
oposed to be put
longing to world
nd offers a man-
age information.
(b) During the fire
(c) An overview of the damages caused by the fire
3. DESCRIPTION OF DATA AND PROCESSING
METHODOLOGY
In order to support a proper and accurate geo-referencing of the
Information System, the first phase was the production of an
accurate and detailed (to the necessary degree) orthophoto-
mapping of the urban structure. Emphasis has been put on the
core part of the historic center, which has been destroyed by the
fire of 1917.
For this reason, recent aerial photography of 1: 20,000 scale has
been used. A total of 39 images have been scanned at a
resolution corresponding to a pixel size of 15 um on the image
plane. The necessary GCPs (Ground Control Points) have been
measured by Ashtec-L1 GPS receiver to a 3D accuracy of 3 cm.
À total of 26 GCPs have been measured (all referred to the
National Reference System) to support the aerial mapping.
LE a tPA de
(d) A close view of the fire damages at the historic center
(e) A view of the current status. The green line denotes
the official borders of the damaged area
Figure 1. The fire of 5-8-1917 and the caused damages at the
historic center of Thessaloniki.
The aerial images have been photogrammetrically processed
(oriented and triangulated) and the earth surface have been
modelled by measured DTM points, which have been photo-
grammetrically collected on a manual mode, due to harsh condi-
tions (high buildings, shadows, etc) in the historical urban cen-
ter of the densely populated city. A total of approximately 400
points have been selected to a height accuracy of 40 cm.
Subsequently, an orthoimage has been produced at a scale of 1:
5,000 with a planimetric accuracy of 35 cm and a ground pixel
size of 50 cm. The orthoimage has been finally draped on the
underlying DTM, in order to produce a 3D visual effect.
Figure 2 shows different views of the greater metropolitan area,
as well as closer views of the part of historic center, relevant to
this research. All views are geometrically corrected extracts
—395—
