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AUTOMATED GENERATION AND UPDATING OF DIGITAL CITY MODELS USING 
HIGH-RESOLUTION LINE SCANNING SYSTEMS 
G. Vozikis 
IPF, Vienna University of Technology, Gusshausstrasse 27-29, 1040 Vienna, Austria 
gvozikis@ipf.tuwien.ac.at 
Commission III, WG 111/7 
KEYWORDS: Databases, Remote Sensing, Automation, Change Detection, Extraction, Building, Satellite, High Resolution 
ABSTRACT: 
During the past few years lots of research has been carried out in the field of building extraction from airborne laser scanner data and 
airborne large-scale imagery. This data can be used to create highly detailed Digital Surface Models (DSMs) and eventually Digital 
City Models (DCMs). It seems that there exists also a potential in data acquired by high-resolution satellites and airborne multi-line 
scanners in order to derive these models. 
Already existing extraction-algorithms for Lidar data cannot be adopted to those spaceborne and airborne imageries since the 
geometric resolution is too coarse. The proposed method can be divided into the following steps. The derived normalized DSM is 
used together with image data to localize potential building areas. Afterwards the building edges and corners are extracted, which is 
carried out with an adaptive region growing process and an iterative step-by-step Hough transformation. Finally, change detection 
techniques and a method for updating existing data-bases in an automated way are discussed. 
KURZFASSUNG: 
Wihrend der letzten Jahre wurde viel Forschung im Bereich der Gebiudeextraktion von Laserscanner- und Luftbildern betrieben. 
Diese Daten werden verwendet um detaillierte Oberflichenmodelle (DSMs) und eventuell auch Digitale Stadtmodelle zu erzeugen. 
Es besteht die Vermutung dass auch bei hochauflösenden Satellitenbildern und flugzeuggestützten Zeilenscanneraufnahmen ein 
gewisses Potential zur Erzeugung dieser Modelle existiert. 
Bereits bekannte Extraktionsalgorithmen aus dem Bereich der Laserscannertechnologie kónnen leider nicht adaptiert werden, da die 
geometrische Auflósung der Satelliten- und flugzeuggestützten Zeilenscanner-Daten zu grob ist. Die vorgeschlagene Methode kann 
in folgende Schritte unterteilt werden. Das abgeleitete normalisierte DSM wird gemeinsam mit den Bilddaten zur Lokalisierung 
potentieller Gebäuderegionen verwendet. Anschließend werden Gebäudekanten und —ecken extrahiert, was durch ein adaptives 
region-growing' und einer iterativen ,Schritt-für-Schritt Hough Transformation geschieht. 
Abschließend werden Methoden zur. Veründerungsdetektion und Instandhaltung von Datenbanken vorgestellt. 
I. INTRODUCTION 
Digital City Models (DCMs) have become one of the most 
important and attractive products of photogrammetry and 
remote sensing. The spectrum of application areas dealing with 
such models is huge: environmental planning and monitoring, 
telecommunication, location based services, navigation, virtual 
reality, cadastre etc. 
During the last decade photogrammetry and remote Sensing 
experienced a big technological advance. On the one hand, 
because the geometric resolution of satellite imagery has 
increased tremendously (footprints of one metre or less are 
current state); on the other hand photogrammetry has become 
more and more 'digital and new techniques are needed to 
accelerate the workflow. Due to this progress the science of 
satellite remote sensing starts dealing with application areas, 
that until now where classical photogrammetric tasks, such as 
large scale mapping or city model generation. 
A challenging goal is to automate and accelerate the production 
of DCMS, to increase their quality and to keep them up-to-date. 
When done manually this procedure is one of the most time 
consuming and expensive tasks. 
1033 
The use of airborne laser scanners and the related processing 
techniques were a big step towards faster city model extraction. 
Though extensive research has been carried out, (e.g. Brenner, 
2000; Haala et al., 1998; Vosselman and Dijkman, 2001) they 
are still affected with certain weak points. Optical systems 
based on multi-line sensor technology (ADS40, HRSC) are able 
to seriously compete with laser scanner systems in some 
application areas. The generation of Digital Surface Models 
(DSMs) from multi-line scanner data has been investigated 
thoroughly (Scholten and Gwinner, 2003) and has reached a 
certain level of practicability. Unfortunately these models are 
so-called raster models; hence the depicted features, e.g. 
buildings, are not classified and without topological 
information. 
Besides airborne acquisition techniques high-resolution 
spaceborne scanners offer a very important data source, since 
they can capture images from nearly any region of the earth's 
surface without having any juridical problems. 
This paper focuses on aspects concerning city model generation 
from both airborne and spaceborne line-scanning systems, 
while it does not deal with the derivation of DSMs from those 
images. By analysing (already existing) DSMs and therefrom