CONCEPTS OF AN OBJECT-BASED CHANGE DETECTION PROCESS CHAIN 
FOR GIS UPDATE 
P. Hofmann, P. Lohmann, S. Müller 
IPI - Institute of Photogrammetry and Geolnformation, Leibniz Universität Hannover, 
Nienburger Str. 1, 30167 Hannover, Germany - (heipke, hofmann, lohmann, mueller)@ipi.uni-hannover.de 
Working Group IV/3 
KEY WORDS: Change Detection, Indicators, GIS, Updating, Satellite Mapping 
ABSTRACT: 
Today, with the situation of rapidly emerging high resolution earth observation data by optical and microwave sensors there is a 
growing need for efficient methods to derive, maintain and revise land cover data at various scales by regional, national and 
European authorities. This paper focuses on parts of a current research project named DeCOVER, namely the change detection which 
is used to identify candidates of change in land-use (LU) or land-cover (LC). The change information needed is automatically 
derived from multi-temporal satellite image data of a spatial resolution of approximate 5m to be comparable to the planned German 
RapidEye system. This paper concentrates on the first outcomes of the implemented process chain, namely the focusing module and 
the segmentation and classification module. The focusing module has two tasks: First, to detect potential changes relevant to the GIS 
database and second, to decide, whether the detected changes and the affected GIS-objects subsequently can be reclassified 
automatically in the segmentation and classification module or must be processed manually. Different change indicators are 
implemented based on a comparison of the input satellite data of two different points of time. These indicators in combination with a 
transition-probability-matrix are used to steer the subsequent process of verifying the indicated changes according to the sorted 
probabilities of change. As a result a change-layer is produced which outlines potential changes relevant to the GIS database (here 
the nomenclature of DeCOVER) and which holds evidence about the plausibility of each detected change. 
1. DECOVER BACKGROUND AND CONTEXT 
In the context of GMES (Global Monitoring for Environment 
and Security), a joint initiative of European Commission and 
European Space Agency, several services are developed to 
provide spatial information in support of the monitoring and 
reporting obligations of European directives (Overview at 
www.gmes.info, Example Water Framework Directive Dworak 
et al 2005). These implementations take place with strong 
participation of German authorities, researchers and service 
providers. Current developments at the European level support a 
new European-wide land cover data set (Core Service Land 
Monitoring). This data set must be seen as a European 
consensus and will solely contain thematic land cover data 
information supporting European reporting obligations. Its 
geometric and thematic resolution will only partly support 
national and regional needs. DeCOVER (Biischer, et al., 2007) 
will complement and extend these developments at the national 
and regional level for German users 
.A set of geo-information services has been designed to support 
national and regional users in their monitoring and reporting 
obligations. The DeCOVER service concept is divided into core 
and additional services. The DeCOVER core service has two 
main focal points. First, the provision of national harmonized 
land cover data supports the German spatial data infrastructure 
(GDI-DE) in providing selected and validated geo-in formation 
and second, the development and application of change 
detection and interoperability methods to sustain existing data 
bases (namely ATKIS, CLC and BNTK). The project is co- 
funded by the Federal Ministry of Economics and Technology 
(BMWI) via the German Aerospace Center (DLR). In a 
coordinated attempt the processing (segmentation & 
classification) of the satellite data is being done according to 
rules and directives as demanded by European and National 
directives and policies. The methods developed and strategies 
used are being implemented for the creation of the core service 
and have direct impact to the processing chain, quality control 
and data revision, considering at each stage the specification 
and standards as demanded by the interoperability task. The 
currently tested object catalogue of the core-service includes 39 
land cover (LC)/land use (LU) classes arranged in a hierarchical 
order. The detailed object catalogue and mapping guide as well 
as a list of collaborating partners can be found in the user portal 
of the DeCover homepage (see DeCOVER, 2008). 
There are three major areas of innovative research and 
development in the project, where methodologies are developed, 
namely 
- the area of semantic interoperability 
- change detection 
- data fusion of optical and SAR images 
In the following this paper will focus only to the second part, 
the change detection. 
2. THE CONCEPT OF DECOVER CHANGE 
DETECTION 
Change detection (CD) algorithms can be classified either into 
the comparison of classes following an interpretation at differ 
ent dates (post-classification) or to image differencing (Singh, 
1989). The former focuses on the comparative analyses of inde 
pendently produced interpretations from different times, the 
latter comprises simultaneous analysis of multi-temporal data. 
Because a second classification of the whole area results in 
costs, far too expensive for most of the users another procedure 
is envisaged here. CD in this case is regarded not as a change 
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