| Catastrophic events like strong earthquakes can cause big losses in life and economic values.
An increase in the efficiency of reconnaissance techniques could help to reduce the losses in
life as many victims die after and not during the event. A basic prerequisite to improve the
rescue teams' work is an improved planning of the measures. This can only be done on the
basis of reliable and detailed information about the actual situation in the affected regions.
Therefore, a bundle of projects at Karlsruhe university aim at the development of a tool for
fast information retrieval after strong earthquakes. The focus is on urban areas as the most
losses occur there. In this paper the approach for a damage analysis of buildings will be
presented. It consists of an automatic methodology to model buildings in three dimensions, a
comparison of pre- and post-event models to detect changes and a subsequent classification of
the changes into damage types. The process is based on information extraction from airborne
laserscanning data, i.e. digital surface models (DSM) acquired through scanning of an area
with pulsed laser light.
To date, there are no laserscanning derived DSMs available to the authors that were taken of
areas that suffered damages from earthquakes. Therefore, it was necessary to simulate such
data for the development of the damage detection methodology. In this paper two different
methodologies used for simulating the data will be presented.
The first method is to create CAD models of undamaged buildings based on their construction
plans and alter them artificially in such a way as if they had suffered serious damage. Then,
a laserscanning data set is simulated based on these models which can be compared with real
laserscanning data acquired of the buildings (in intact state).
The other approach is to use measurements of actual damaged buildings and simulate their
intact state. It is possible to model the geometrical structure of these damaged buildings
based on digital photography taken after the event by evaluating the images with
photogrammetrical methods. The intact state of the buildings is simulated based on on-site
investigations, and finally laserscanning data are simulated for both states. |