Geoscience Reference
In-Depth Information
3 The Update Concept
3.1 Closing the Gap Between Old LiDAR-Data
and New Built Buildings
The airborne laser scanning data gained by statewide LiDAR-campaigns in Bavaria
is up to 7 years old in particular areas. Beyond that Bavaria is covered with digi-
tal aerial photographs in a 3 year cycle. The ground pixel size of the aerial photo-
graphs is approximately 0.2 m. The oriented aerial photographs are also supposed
to be used for the acquisition of the 3D Building Model.
The timed space closure means the later acquisition of buildings for which, at the
moment of the first acquisition with automatic building reconstruction from LiDAR-
data, the building ground plans from the land registry, but not the height informa-
tion from LiDAR-data was available. Since the building ground plans from the land
registry usually are more actual than the LiDAR-data, new buildings which were
built after the LiDAR-campaign, are the ones which are affected by the timed space
closure. Buildings for which, at the time of the first acquisition, height information
from LiDAR-data was available, but no building ground plans in the land registry,
were not reconstructed.
In order to close the actuality gap of the up to 7 years old LiDAR-data within
the data capturing of the 3D Building Models, a DSM from image correlation
(Image Matching) of aerial photographs from the Bavarian surveying flight is pro-
cessed. The Bavarian photogrammetric campaign is carried out with an overlap of
75 % in longitudinal and 30 % in cross direction.
In Bavaria the point density of current LiDAR-campaigns is 4 points per square
meter. With Image Matching it is possible to reach a significant higher point den-
sity of up to 25 points per square meter due to the ground pixel size of 0.2 m of
the Bavarian Photogrammetry flights. Currently, the software MATCH-T from
Inpho and the Surface Reconstruction (SuRe) algorithm from the Institute for
Photogrammetry (ifp) of the University of Stuttgart are used to calculate a DSM
on basis of the current Bavarian Photogrammetry flights for several areas of
Bavaria (Stolz
2013
). In particular, Image Matching got a significant impulse from
Semi-Global Matching (SGM) Algorithm (Haala
2011
).
The difference between the LiDAR-data processed in 2007 and data from
Image Matching from aerial photographs of the Bavarian Photogrammetry cam-
paign in 2012 can be easily presented in a differential-DSM. All changes in height
between the years 2012 and 2007, like the growth of the vegetation, the construc-
tion and demolition of buildings, excavation pits and earthworks can be visualized
with an appropriate color scale.
The situation for the maintenance of the 3D Building Model within the timed space
closure is as follows: Fig.
7
shows a differential-DSM. Within the marked circle a major
change of a building has been identified. Considering the color scale it becomes clear,
that it must be a newly built building due to the negative (red) height difference. In this
case it is a construction of a shopping center in the year 2009, as it is shown by the com-
