1091 
GENERATION OF COARSE 3D MODELS OF URBAN AREAS 
FROM HIGH RESOLUTION STEREO SATELLITE IMAGES 
Thomas Krauß, Manfred Lehner, Peter Reinartz 
German Aerospace Center (DLR), Remote Sensing Technology Institute 
PO Box 1116, 82230 Wessling, Germany, thomas.krauss@dlr.de 
Commission I, WG 1/5, ThS-3 
KEY WORDS: digital terrain model, surface modelling, stereo image, high resolution, optical satellite sensors, image matching, 
classification, contouring, visualization, information extraction 
ABSTRACT: 
With the emergence of more and more satellites delivering very high resolution (VHR) imagery with ground sampling distances in 
the range of one meter or below the generation of three dimensional urban models directly from space may become possible. Such 
models are required for many applications in areas where no up-to-date detailed urban mapping exists like in developing countries. 
Besides the creation and updating of maps from sprawling urban settlements, such three dimensional models are also very useful for 
simulation and planning. For example simulations of catastrophic events like flooding, tsunamis or earth quakes rely on digital 
terrain models (DTM) populated with three-dimensional man made and natural objects. Using VHR satellite imagery is often the 
faster and cheaper alternative to acquiring aerial photos or even laser DEMs or in some times even the sole source of information for 
remote areas. In this paper a method for an automatic processing chain for urban modeling based on stereo images from VHR 
satellites is proposed. After import and preprocessing of the images a digital surface model (DSM) is derived from the stereo data. 
Subsequently a digital terrain model (DTM) and true ortho images are generated based on the DSM. Using a high objects mask and a 
vegetation mask based on the normalized difference vegetation index (NDVI) a coarse classification will be derived and suitable 
models for the detected objects (e.g. houses, trees, ...) are selected and finally the 3D models get exported in a suitable format like 
VRML. 
1. INTRODUCTION 
The launch of WorldView-I on the 18 th of September 2007 
added a new member to the fleet of very high resolution (VHR) 
earth survey satellites. VHR satellite images with ground 
sampling distances (GSD) in the range of 0.5 to one meter are 
now available from Ikonos-2 (launch 24.09.1999, GSD pan 
1 m, multispectral (MS) 4 m), QuickBird (launch 18.10.2001, 
GSD pan 0.6 m, MS 2.4 m), OrbView-3 (GSD pan 1 m, MS 
4 m 06/2003-03/2007), and WorldView-I (GSD pan 0.5 m). 
Also some more systems are planned for the near future like 
GeoEye-1 (planned launch mid 2008, GSD pan 0.4 m, MS 
1.65 m, (DigitalGlobe, 2008)), WorldView II (2009, GSD pan 
0.5 m, MS 1.8 m), or the Pleiades-HR (2010, GSD 0.7 m, MS 
2.8 m). 
Imagery with such high resolutions allow for the first time the 
generation of high resolution urban models directly from space 
for nearly every point on earth. Throughout the following 
investigations Ikonos VHR stereo image pairs were used. 
Already in 2001 C. S. Fraser showed that Ikonos stereo 
imagery has the potential for high resolution building 
reconstruction (Fraser et. al., 2001). A semi automatic 
approach can be built upon such VHR data with rather good 
results. However only few papers exists on fully automatic 
processes for extraction of urban objects from high resolution 
satellite data. 
In contrast many approaches exist for city modelling from 
high resolution aerial imagery, laser scanner data, or semi 
automatic modelling from high resolution imagery. For a short 
overview or further information please refer to (Brenner, 2003) 
or the Ascona proceedings (referenced also in Brenner, 2003). 
These methods are mostly based on cadastral data, aerial 
images, aerial and terrestrial laser scanner data, terrestrial 
photographs and more additional information since the aim of 
these methods are often near photorealistic city models in 
industrial countries integrating data from several sources in 
often intense manual work for the urban models (CyberCity, 
2008, 3D Geo, 2008). For the future Pleiades satellites 
(Flamanc, 2005) proposed a framework for the generation of 
3D city models using a digital surface model (DSM) and a true 
ortho image generated from the high resolution satellite data 
together with 2D footprints of the buildings. 
In contrast we want to propose a (mostly) automatic method 
for deriving 3D city models from only one single stereo scene 
of any area in the world. So no additional data besides the two 
VHR stereo images will be available since the results should 
also be usable for rapid mapping purposes in catastrophic 
events. 
In this case only coarse city models with a level of detail 
between LoD-1 and LoD-2 will actually be needed. Following 
the definition in (CityGML, 2008) LoD-1 describes a block 
model with buildings as polygons with only a flat roof and 
LoD-2 describes buildings with a more detailed outside cover 
including more detailed roof structures and simple textures. In 
our case a coarse distinction between buildings with flat roofs 
and gabled roofs but no more roof details may be possible 
depending on the quality of the generated DSM.