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2011 IEEE Com-
EXTRACTING SEMANTIC BUILDING MODELS FROM AERIAL STEREO
IMAGES AND CONVERSION TO CITYGML
A.Sengul *
? ITU, Civil Engineering Faculty, Dept. of Geomatic Engineering, 80626 Maslak Istanbul, Turkey ahmetsengul@gmail.com
Commission III, WG IV
KEY WORDS: 3D City model, CityGML, Data model
ABSTRACT:
The collection of geographic data 1s of primary importance for the creation and maintenance of a GIS. Traditionally the acquisition
of 3D information has been the task of photogrammetry using aerial stereo images. Digital photogrammetric systems employ
sophisticated software to extract digital terrain models or to plot 3D objects. The demand for 3D city models leads to new
applications and new standards. City Geography Mark-up Language (CityGML), a concept for modelling and exchange of 3D city
and landscape models, defines the classes and relations for the most relevant topographic objects in cities and regional models with
respect to their geometrical, topological, semantically and topological properties. It now is increasingly accepted, since it fulfils the
prerequisites required e.g. for risk analysis, urban planning, and simulations. There is a need to include existing 3D information
derived from photogrammetric processes in CityGML databases. In order to filling the gap, this paper reports on a framework
transferring data plotted by Erdas LPS and Stereo Analyst for ArcGIS software to CityGML using Safe Software's Feature
Manupulate Engine (FME)
1. INTRODUCTION
1.1 General Information
Virtual 3D city models gain more and more importance in
Science, government, and private industry. Several
municipalities decide nowadays to build up 3D city models in
order to clearly understand the cities' real situations. With the
increasing number of more complex applications and objectives
more sophisticated models are required not only based on
geometric information, but on semantic information as well as
on 3D topology, representing the meaning and functionality of
urban objects. CityGML, an OGC standard for city and
landscape modelling, is able to identify structures for the
organization of urban information which can be used in a broad
range of applications, e.g., for analysis in urban planning,
disaster management, and environmental simulations.
Traditionally, acquisition of 3D objects is done by
photogrammetric methods, using aerial stereo images. Leica
Photogrammetrry Suite (LPS) by Erdas for example, offers
sophisticated tools for stereo feature collection. But there is a
gap between the photogrammetric measurement and the storage
of processed objects in CityGML which is filled by a student’s
master thesis completed at the Technische Universitit Berlin.
2. 3D CITY MODELLING
2.1 3D City Models
3D City Models are digital representations of the Earth’s
surface and related objects belonging to urban areas. In order to
get information about a city it is necessary to collect data from
different sources. There are several methods of collecting the
data such as LIDAR, laser scanning, surveying measurements,
aerial and satellite images. ..etc.
2.2 Semantic 3D City Models
Semantic 3D city models comprise besides the spatial and
graphical aspects particularly the ontological structure including
thematic classes, attributes, and their interrelationships. It
follows structures that are given or can be observed in the real
world. For example, a building can be decomposed into
different building parts, if they have different roof types and
their own entrances like a house and the garage (Kolbe,2009).
3.DATA MODELLING
Data modelling defines the relationships between data elements
and structures. Data modelling techniques are used to model
data in a standard, consistent, predictable manner in order to
manage it as a resource (Carlis, 2001).
3.1 Building model in photogrammetric tools
The photogrammetric tools are combined with ERDAS Imagine
— LPS and ArcGIS Stereo Analyst in the thesis work. The
building data model of ERDAS which could not reach
anywhere and it decided to build using UML diagram.
Modelling the UML diagram of the ERDAS Imagine LPS
module and ArcGIS Stereo Analyst is another task to follow on
the project, while working on the photogrammetric methods.
The UML diagram will help the user to follow the thesis work.
It is representing the details of the workflow (Fig3.1).
