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Title
New perspectives to save cultural heritage
Author
Altan, M. Orhan

CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
The equations (l.a or l.b) have to be firstly linearized; in this
way it is possible to solve system 2 through a least square
solution:
V = PA-x-P-L
X = (a t -P-a)'-A t P L <2>
The first problem to face is the ill conditioning of the system
that is obtained from the previous linearization. The Tikhonov
regularization algorithm was used to solve the problem. As
known, it is based on the addition of a small empiric coefficient
(l 2 ) to the diagonal elements of the A T PA normal matrix . The
following system can be written:
X = (a t -PA + X 2 ■/)"'-A 7 PL (3)
The Royal Palace of Venaria has been declared a Property of
Humanity by U.N.E.S.C.O.
It was built by Castellamonte in the late 17 th century and it
consisted of a village, royal palace and gardens and extended
for an axis of 2 km. The building works were then assigned to
the architect Juvarra in the early 18 th century.
Figure 2. Royal residence in Venaria (Turin)
2.2 Images, D.E.M. and cartography
This operation forces the system to converge after a few
iterations.
The second problem is the occurrence of some asymptotes
during the use of polynomials. An over parametrization test
was carried out to evaluate which coefficients have to be used in
the transformation. Firstly a x 2 iest was carried out to
understand whether raw errors are present or whether the model
is overparametrized. If overparametrization is detected, further
analyses (t Student tests) are performed to identify the
coefficients that can be neglected.
It was found that both the number of coeffiecient to be used and
the ill conditioning of the system are closely related to the
geometric distorsion due to the sensor attitude and to the
elevation range of the scene.
2. AVAILABLE DATA
2.1 Test site
Two test sites were chosen in the outskirts of the city of Turin
(Piedmont, Italy): Stupinigi (fig. 1) and Venaria Reale (fig. 2).
These represent two Italian cultural sites as they are old
residences. Stupinigi was built in the first half of 18th century
by the architect Juvarra as a hunting lodge and residence for the
Savoia family; it is the nucleus around which a National Natural
Park develops. An ancient medieval castle, Castelvecchio,
which is well preserved, can be found near the hunting lodge.
A Spot 5 panchromatic oversampled image and a QuickBird
panchromatic one were considered for two different scale
analyses. Correspondent multispectral bands were also available
for both the images. The main features of these images are
shown in table 1.
Spot 5
QuickBird
Date (dd mmm yyyy)
01 Oct 2002
22 Sep 2002
Pan Resolution (m)
2.5 (supermode)
0.61
XS Resolution (m)
10.0
2.44
Level
IB
IB
Table 1 - Remotely sensed images available of the test site
The Digital Elevation Model of the Piedmont Region was used
during data processings. This model is characterized by a 50m x
50m grid and an accuracy of ± 5m.
According to the expected scale mapping (which mainly
depends on the geometric resolution of the images) the
following cartographic reference data were used:
• vector 1:10000 scale Technical Regional Map (CTR,
used for orthocorrection of the SPOT image);
• raster 1:5000 scale Technical Provincial Map (CTP,
used for orthoprojection of the Quickbird image).
These data were adopted to collect the Ground Control Points
(GCP): Check Points (CHP) have instead been collected on
larger scale maps (1:5000 and 1:2000) here called Test
cartography.
Reference cartography photogrammetric flights were made in
1991 (CTR) and 1993 (CTP). This fact permits us to face the
updating problem as the area of interest has been subject to
intensive changes over these years. Our interest in particular is
to demonstrate that satellite high resolution images can be
useful:
• to investigate any modifications that have occurred in
the cultural sites, such as heavy restoration and
requalification activities;
• to investigate the management of the surroundings
devoted to the context in which the cultural sites are
situated.
3. ACCURACY TESTS
Figure 1. Royal hunting lodge and national park in Stupinigi
(Turin)
In order to proceed with a correct updating test, we paid
attention to the accuracy of the positioning (planimetrie)
problem. It is necessary to say a few words about such problem