The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008
be rectified to the main plane of the facade. Therefore, the plane
was defined by more than three points, which were measured in
the point cloud and in the image. Thus, the photos were
rectified to the main plane of the facades and shifted to parallel
planes based on the point clouds. Based on the dense point
clouds from the Leica HDS4500 scanners, the mapping was
often possible without support of the photos, using just the grey
values of the point cloud. Nevertheless, the colour photos are a
significant support particularly for the detailed mapping of
bricks and stones (see Figure 10). One major problem is the
very detailed mapping of bricks and stones, which reduced the
speed of mapping significantly. Unfortunately, the architects as
the major clients could not be convinced to use digital
orthophotos of the facades instead of the detailed maps in the
scale of 1:200. An example of the final product from façade
mapping is depicted in Figure 11, which is derived from 3D
polylines as illustrated in Figure 12. Currently, the mapping of
the building facades is still not finished.
Figure 10. Detailed mapping of a building façade based on
laser scanning data and a photogrammetric image
25? Ada Tarakçîiar H&m Sokak RôSôvesi
Figure 11. Part of the final product from façade mapping using
terrestrial laser scanning data and photogrammetric images
Figure 12. Mapped 3D polylines of facades of a building block
6. ROOF MAPPING
Since early July 2007 a roof mapping group was established, in
order to measure and to model the roofs of all buildings in 3D
within the perimeter of the Historic Peninsula project. A project
team of five operators started the new production line after
three days of intensive training in mid July using the Z-MAP
Foto software (Figure 13). In the beginning UltraCamD images
with 30cm GSD were used for data acquisition. Due to the
limited resolution of the digital imagery it was very difficult for
the operators to measure small roofs. As a rule of thumb,
mapping is possible up to the map scale 1:3000 with 30cm
ground sampling distance (GSD), which could be confirmed by
the tests made in this group. Thus, it was decided to use higher
resolution imagery for this task, available since mid August as
scanned analogue colour aerial images with 9.5cm GSD. The
photo flight has been conducted using a JenOptik LC0030
camera (f= 305mm) at a photo scale of 1:4500. The photos were
scanned with a resolution of 21 pm using a Zeiss SCAI scanner.
Figure 13. 3D mapping of roofs using Menci-software Z-MAP
Foto in stereo mode
In this part of the project an essential quality-defining task was
the combination of the two different data sets, from aerial
imagery and mobile TLS, into one common data set in the same
coordinate system without any discrepancies caused by the
different data acquisition sources. Therefore, the orientation of
the aerial images was transformed into the same datum as was
used for the laser scanning data, in order to perform the
mapping in the same coordinate system. The differences
between façade comers and roof comers are mainly in the range
of 20-60cm (spatial vector). The differences mainly represent
the effect of point definition - the roof extends over the wall. In
addition the following error sources exist: effects from datum
transformation, accuracy of the orientation data, accuracy of the
laser scanning data, identification of the roof comers in the
images, definition of the roof comer and facade comer (rain
spout), respectively. The two last sources for discrepancies
might have the biggest influence on the accuracy of the merged
data, which is generated from data of two different sensor