The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008
Figure 4. 3D polylines map of building facades based on Z-
MAP Laser
The production rate varied between 60 m 2 facade/day/operator
(March 2007) and 140 m 2 /day/operator (October 2007), which
is an increase of production speed by a factor of more than 2. If
one assumes in total 5 Mio m 2 façade areas for mapping of the
Historic Peninsula, it corresponds to an estimated mapping time
of approximately five years with 34 operators working on 210
days per year.
An example of the final product from façade mapping is
depicted in figure 6, which is derived from 3D polylines as
illustrated in figure 5. The mapping of the facades is described
in more detail in Baz et al.,(2008).
Figure 5. Mapped 3D polylines of building block façades
derived from terrestrial laser scanning data
Figure 6. Detailed map of building façades using laser scanning
data - laser scanning data (top) and façade plan (bottom)
5. ROOF MAPPING WITH AERIAL IMAGERY
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 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.
In the beginning available UltraCamD images with 30cm
ground sample distance (GSD) were used for data acquisition.
The synthetic UltraCamD image has 7500 x 11500 pixels with a
pixel size of 9pm*9pm corresponding to an image format of
67.5mm in the flight direction and 103.5mm across flight
direction and a focal length of 101.4mm. Each image covered
2.3km x 3.5km.
The photo coordinates have been determined by automatic
aerotriangulation with an Intergraph workstation, while the
orientation elements of the digital images were adjusted by
bundle block adjustment with BLUH. The results of the bundle
block adjustment with self-calibration of the UltraCamD data
are summarised in (Büyüksalih and Jacobsen,2006). A
horizontal accuracy of up to a factor 0.6 of the GSD could be
achieved at independent check points, which corresponds to
18cm in object space. This is a limited result for a digital
camera. The sigmaO from the bundle block adjustment is in the
range of 0.4 pixels, indicating that the accuracy potential is
better. The main reason for this is the limited control point
definition and accuracy. Nevertheless the achieved geometric
quality is sufficient for the roof mapping, which is more limited
by the object definition. The vertical accuracy is two times
better than the horizontal accuracy due to good connections
between the images in the block and due to measurements of
each control point in 4.5 images (on average).
However, due to the limited resolution of the UltraCamD
imagery it was very difficult for the operators to measure small
roofs and to identify clearly the roof points. As a rule of thumb,
mapping is possible up to 0.1mm GSD in the map scale,
corresponding to a map scale of 1:3000 with 30cm GSD, which
was confirmed by the tests made by this group. Thus, it was
decided to use higher resolution imagery for this task, available
since mid of August as scanned analogue colour aerial images
with 9.5cm GSD. The aerial flight has been conducted using a
JenOptik LC0030 camera (f = 305mm) in July 2006 at a photo
scale of 1:4500 covering almost 1 km 2 per photo. The photo
orientation was determined by automatic aerial triangulation
and bundle block adjustment. The expected standard deviation
is Sxy = 10cm and Sz = 14cm for topographic points, which is
much better than from the triangulation of the UltraCamD
images. The analogue photos were scanned at a resolution of
21 pm using a Zeiss SCAI scanner. As an example a part of an
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