In: Wagner W„ Szäkely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
644 
CHANGE ANALYSIS WITH TERRASAR-X DATA 
D. Weihing 3 ’ *, F. von Poncet 3 , M. Schlund b , O. Lang 3 
3 Infoterra GmbH, Claude-Domier-Strasse, 88090 Immenstaad, Germany - (Diana.Weihing, Felicitas.Poncet, 
01iver.Lang)@infoterra-global.com 
b Department of Geography, University of Jena, Germany - Michael.Schlund@uni-jena.de 
Commission VII 
KEY WORDS: Analysis, Change Detection, Monitoring, Change, SAR 
ABSTRACT: 
Change analyses play an important role for different applications, ranging from small- to large-scale monitoring. To identify changes 
from SAR images of repeat pass acquisitions different methods are commonly applied, which differ with respect to the parameter as 
an indicator of changes. The backscatter intensity is analysed in incoherent change detection methods, whereas in the coherent 
change detection the complex correlation coefficient is analysed as a change indicator. These methods provide complementary 
characterisations, since they are sensitive to different measures of a SAR scene. 
However, often not only the detection of changes, but also the assessment of the detected changes is of interest, which automated is a 
challenging task. 
In this paper a combination of detection and assessment of changes is shown. Additional information is integrated into the proposed 
scheme to separate relevant changes from less relevant ones in order to decrease unrequested changes and evaluate the type of 
change. Texture measures provide information on the spatial variation of the backscatter and thus information of the local surface 
characteristics within the scene. This information is used to restrict the search for areas and changes of interest as well as for the 
assessment of changes. 
The goal of our analysis is to support the implementation of an operational change detection process and to define a suitable 
assessment of changes from TerraSAR-X data regarding different customers’ requirements. 
1. INTRODUCTION 
In many different geoinformation applications, the detection 
and assessment of changes is of much interest. These 
applications can vary from specific site monitoring to large- 
scale assessment after certain events and for updating existing 
geoinformation databases. 
Satellite SAR missions like TerraSAR-X entail potential for 
such applications, not only because of the large coverage in 
combination with high resolution, but also due to the 
independence regarding daytime and weather conditions. 
The identification of changes implies a comparison of datasets 
or knowledge about a scene of different dates, like e.g. updating 
of existing geoinformation with recent remote sensing data. 
Different approaches for change detection have been studied 
depending on the sensor and available data. 
In this paper the focus is set on the image-to-image change 
detection with TerraSAR-X data, and in particular on repeat- 
pass images with the same acquisition parameters, which allow 
a direct comparison. Therefore, acquisitions of pre- and post 
events are required. 
Detecting changes means that every variation causing a 
different echo signal/backscatter is detected. However, often 
customers are only interested in relevant changes concerning 
their applications. To be able to offer the user-specific change 
information, an assessment of the detections is required. The 
preferably automatic detection and assessment is a goal for a 
worldwide operational process and service. The integration of 
additional information, like e.g. GIS data, in such a process can 
be helpful for this purpose. However, in many regions often this 
required a-priori information is missing or not available in the 
time frame for rapid assessment. Therefore, the used pre- and 
post-event imagery for change detection as a single source has 
to be exploited also to asses the changes. Hence, different 
measures have to be educed from the images to derive more 
information about the scene. 
2. CHANGE DETECTION 
Change detection based on SAR images has been subject in 
different publications. To identify changes from SAR images of 
repeat pass acquisitions different methods are commonly 
applied. These methods differ with respect to the parameter 
which is used to indicate changes and the method to reduce the 
noise. Since SAR data contains amplitude and phase 
information, both parameters can be used as change indicators. 
A common method is the analysis of the radar backscatter 
intensity in time to identify changes between different 
acquisitions, also called incoherent change detection (Preiss et 
al., 2003). This power change estimate is affected by the 
speckle noise component, whose reduction is discussed in 
several publications, e.g. in (Schmitt et ah, 2009). 
Corresponding author.