O
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
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" 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” century.
th
Figure 4. Royal residence in Venaria (Turin)
2.1.1 Dem And Reference Map
A Spot5 panchromatic oversampled image has been considered.
The main features of this image are shown in table 1.
Spot 5
Date (dd mmm vyyy) 01 Oct 2002
Pan Resolution (m) 2.5 (supermode)
XS Resolution (m) 10.0
Level IB
Table 1 — Remotely sensed images available of the test site
The Digital Elevation Model of the Piedmont Region was used
during process. This model is characterized by a 50m x 50m
grid and a vertical accuracy of + 2.5m.
According to the expected scale mapping (which mainly
depends on the geometric resolution of the images) the vector
1:10000 scale Technical Regional Map (CTR) has been used as
reference.
212 Accuracy Tests
In order to proceed with a correct updating test, we paid
attention to the accuracy of the positioning (planimetric)
problem. It is necessary to say a few words about such problem
to underline that a correct geometric positioning of the objects
is as important as the recognition of their modifications.
A detailed statistical analysis was carried out to evaluate which
map scale the obtained orthoimage is suitable for, taking into
consideration the map tolerances (in Italy the usually accepted
value is of 0.2 mm at the map scale and the tolerance is
interpreted as two times this value). This means that a 1:10000
map has a 4 m tolerance and a 1:5000 map has a 2 m tolerance.
Residuals can been considered as statistical variables (one for
each test) and some their statistical features can calculated.
Table 2 shown such values both for the RFM and MLP
approach applied to the SPOTS image.
N° N° AS An RMSE | RMSE
Method GCPs | CHKs mean mean CHK GCP
CHK CHK | (pixel) | (pixel)
RFM 50 5 -0.02 -0.09 2.09 1.01
MLP NN 50 5 -2.04 0.02 2.96 1.38
Table 2 — Accuracy tests results obtained with the RFM and
MLP NN self-developed orthoprojection routines on the SPOTS
image.
Fitting statistical tests have also to be made on each residuals
distribution in order to understand whether it would fit a normal
statistical distribution or whether it is affected by systematic or
raw errors. In particular, the y^ test was performed. The
residuals successfully passed this test.
Considering RMSE values it is possible to say that Spot5
orthoimages, obtained with well trained generic methods, are
geometrically suitable for a 1:10000 scale map updating.
2.1.3 Map Updating
A geometric answer gives indications on the scale of the map.
But what about the image contents? Are particulars that are
really changed distinguishable? Can they be correctly digitised?
How can building relief displacement limit the graphical
reproduction?
It is the authors opinion that visual interpretation of
orthoprojected images can effectively be used for planimetric
updating of any available cartography (depending on the map
scale).
The simple adopted process is based on an accurate visual
comparison between the reference cartography and the
orthoprojected image; cartography overlapping onto the
orthoimage is a simple and useful tool to proceed with the
digitisation of the elements that are not present or changed.
The following three figures show the area of the Venaria Reale
Gardens that is at the moment being restored: in this example
the new positions and shapes of the gardens have been updated
on the Regional Technical Map (1:10000)
The same example can also be used to demonstrate how the past
territorial management damaged an important cultural site,
permitting sports and factory buildings to be built in the
immediate surroundings of the palace. A satellite orthoimage
can therefore be considered an economic evaluating tool in the
hands of administrative bodies.
Figure 5. Spot 5 image (2.5m) of the Venaria Reale area
1069
