The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008
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historical protected areas. The Historic Peninsula (Fig. 1)
comprises an area of 1500ha with approximately 48,000
buildings in crowded and frequently narrow streets (total length
400 km). The facades of the building along the roads and streets
cover an area of about 5,500 000 m 2 . In 2003 it was completely
declared as a protected area, when urban protection plans at
1:5000 and 1:1000 map scales were completed. For these
protected areas detailed studies of urban design projects based
on 1:500 and 1:200 map scales shall be carried out in the future.
A project contract, briefly named as “Historical Peninsula
project” was allocated to BIMTA$ by the Istanbul Greater
Municipality’s Directory of the Protection of Historical
Environment. Finally, due to the request of many municipality
applications and due to an expected earthquake in Istanbul
within the next 30 years BIMTAS, a company of the Greater
Municipality of Istanbul, started the documentation of all
buildings in the Historic Peninsula area by terrestrial laser
scanning in 2006. It has been planned that the Historic
Peninsula should be mapped in a time frame of two years,
which demonstrates the great ambition of the project.
The data acquisition of the Historic peninsula was carried out
by terrestrial laser scanning for the building facades in the
streets and for the building roofs by aerial photo flights with an
analogue and a digital camera.
3. DATA ACQUISITION BY TERRESTRIAL LASER
SCANNING
The data acquisition by terrestrial laser scanning started in
September 2006 mainly using four Leica HDS4500. Figure 2
shows an example of a coloured point cloud of building facades
in the Historic Peninsula. 80ha of the project area (of 1500ha in
total) was scanned within the first six months using the existing
production capacity, which clearly indicated, that the scanning
would need more than eight years for the entire project area, if
this current scan rate of approximately 0.7ha per day could not
be increased.
calibration of the system in the streets of Istanbul took some
weeks, but the data acquisition in the field has been working
since the end of June 2007. The laser scanner was fixed with its
orientation in the horizontal direction, scanning only in the
profile perpendicular to the moving direction and operating
with a speed of up to 40 profiles/sec. The distance between
neighbouring profiles was 2-3 cm at the beginning,
corresponding to a speed of the van during scanning of
0.5m/sec up to 0.75m/sec or 1.8 km/h up to 2.7km/h.
Figure 3. Sensor configuration on the mobile mapping van of
VISIMIND AB
Thus, the speed of data acquisition by terrestrial laser scanning
was significantly increased through use of this mobile mapping
system. Consequently, the laser scanning with the mobile
system was finished by November, 8 th , 2007 with the improved
total production rate of ~600m per hour, while post processing
of the multiple sensor data took until January 2008. The
production rate was mainly 1:10, i.e. for one hour scanning 10
hours post processing of the data was needed. However,
approximately 2% of the area (30ha) could not be scanned by
mobile TLS due to traffic restrictions and environmental
conditions. For the scanning of this remaining part static TLS is
required. A more detailed description of the data acquisition by
terrestrial laser scanning for the Historic Peninsula project is
summarised in Baz et al.,(2008).'
4. MAPPING OF FACADES
The geo-referenced point clouds from laser scanning were used
for line mapping of the facades at a scale of 1:200. The required
positional standard deviation of 0.2mm on the map corresponds
to 4cm in the object space as relative accuracy. The facade
mapping was carried out by 34 operators using the Menci-
software Z-MAP Laser from Italy, which is able to process laser
scan data and rectified photogrammetric images simultaneously
for line mapping with limited AutoCAD functionality. An
example for the mapping of building facades with Z-MAP
Laser is shown in Fig. 4.
Figure 2. Coloured point cloud of building facades in the
Historic Peninsula
As a consequence the static scanning was replaced by mobile
mapping through the Swedish company VISIMIND AB (Fig. 3)
in June 2007 using a hybrid sensor system on the vehicle
consisting of a terrestrial laser scanning system HDS4500,
supported by GPS/IMU and digital cameras. This increased the
scan rate dramatically. The sensor integration and the