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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004
Figure 1. Pavia’s GPS and levelling networks. Blue triangles
are the GPS network vertices, red circles represent levelling
benchmarks, green lines are levelling paths. The black triangle
represents the GPS permanent reference station
Min Max Mean Std
e 0.12 0.44 0.220 0.097
n 0.09 0.42 0.181 0.097
u 0.42 1.28 0.607 0.237
Table 1. Mean statistical parameters of standard deviations s of
the network vertices, referred to a local Cartesian coordinate
system, measured in centimetres
The greater part of the network's points have been connected
by geometric levelling, so that we know, for each levelled point
of the network, the ellipsoidal height, as well as the orthometric
height. This allowed us to estimate a very detailed model of
geoid undulations: we verified that its mean square error is
around four centimetres.
4.2 Cartography
There are many different cartographies concerning Pavia. Their
scales range from 1:500 to 1:100.000. Table 2 summarizes the
main features of those characterized by large/medium ratio
scale.
Produc-
Scale support covered Owner tion/last
ype area update
ee f City Cen- | y viacity 1984
raster tre
The
12000 | Paper& | whole | \Paviacity | 1982/2000
vector city terri-
tory
Paper & m The
1:10000 | ?P*! woe Lombardia | 1983/1994
raster regional uas
region
territory
Table 2. Main characteristics of the available cartographies con-
cerning Pavia
Moreover we have a colour orthophoto whose GSD is 12 cm,
produced in the year 2000 by the Italian company CGR within
893
its Terraltaly City program. The company kindly granted us the
use of the photographs, free of charge.
4.3 Lidar datasets
There are several lidar datasets acquired with different sensors:
Optech 1210, Toposys I, Optech 3033.
4.4 Check areas for lidar datasets
There are check areas constituted by GPS and classical ground
surveying measurements of flat areas, such as tennis courts and
car parks, and of ramps.
Figure 2. Example of a flat
check area
Figure 3. Example of a check
area constituted by a ramp
4.5 The AGCPs set
The first set of ground control points is constituted by 169 arti-
ficial ones which are white squares of 35 cm. They homogene-
ously cover the whole test site, which is 6 x 4.5 km wide.
Figure 4. Distribution of the AGCPs over the test site
The aerial images which have been acquired over Pavia have
scales of 1:5000, 1:8000 and 1:18000, which are generally used
in Italy to produce maps at the scales 1:1000, 1:2000 and
1:10000. The size of the markers has been carefully tuned in
order to have optimal vision on aerial images whose scale is in
the range 1:5000 — 1:8000. Nevertheless, the markers are usu-
ally visible on the 1:18000 images, although with difficulty.
Prior to the creation of the complete set of markers, we created
a couple of test sites, constituted by samples of different sizes
and shapes, shown in Figure 5 and Figure 6.
