ats are responsible for the topography of the lake basin and of
its bed, its valley sides, and the downstream morainal deposits.
Table 1 - Technical data concerning the high altitude aerial
photo coverage of Italy of 1994
Item Data
Area covered 301,200Km° (all of Italy)
Direction of flight axes | E-W and W-E superimposed on the
axes of the 1:25000 scale maps of
the national cartographic agency
(IGM)
Km of flight about 31,000
Relative flight altitude | 11,500m
Average photo scale 1: 75,000
Number of photos 5,500 (overlap 60%, sidelap 20%)
Film used (negative) | KODAK PANATOMIC X
Camera WILD RC 30 equipped with FMC, f
- 152.82mm
Aircraft Lear Jet 25C
Image resolution Between 0.5 and 1m
3.0 High altitude airphoto coverage of Italy
The aerial photography needed for the preparation of the digi-
tal orthophotos of the lake Garda basin were taken from high
altitude photography executed in 1994 by the Compagnia Ge-
nerale Ripreseaeree of Parma. Although in 1988-89, for the
first time, all of Italy was photographed from about 12.000m it
was only in 1994, in a period of about 90 calendar days, and
therefore almost synchronously, that the best photographic co-
verage was acquired with the material and equipment descri-
bed in table 1.
The quality of the photographs was such that it was possible to
achieve operational cartographic quality anywhere in Italy at
the scale of 1:10.000 while meeting the standard specifications
required for that scale.
4.0 Sidescan sonar imagery of lake Garda's bottom
In October, 1994 the floor of lake Garda.was surveyed during
a collaborative project between the US Geological Survey and
the CISIG using a SIS-1000 Seafloor Mapping system and
echosounder. SIS-1000 subsystem include s a sidescan sonar
and Chirp subbottom profiler. The sidescan sonar operated in
the 100kHz band and provided ranges up to 750m to each side
of the sonar vehicle. The data were logged digitally, and pixel
size varied with the swath width used, but was less than 50cm
in the across track direction. The chirp subbottom was a
swept-frequency system with a central frequency of 3.5kHz.
Bathymetry was measured with an ODOM DF 3200 digital
fathometer with the depths being logged with the navigational
information. Ship navigation was done by differential GPS
with two shore stations; one near Riva at the northern end of
thelake and the second at Sirmione at the southern end of
the lake.
Figure 2 - Sidescan sonar image of upper lake Garda floor
showing traces of its inlet. Notice the patterns of sand dunes
formed in the channels.
Figure 3 - Sidescan sonar images of large debris apron on we-
stern side of upper lake Garda
290
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
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