Kristin Spröhnle

Earth Observation-Based Dwelling Detection Approaches in a Highly Complex Refugee Camp Environment — A Comparative Study

For effective management of refugee camps or camps for internally displaced persons (IDPs) relief organizations need up-to-date information on the camp situation. In cases where detailed field assessments are not available, Earth observation (EO) data can provide important information to get a better overview about the general situation on the ground. In this study, different approaches for dwelling detection were tested using the example of a highly complex camp site in Somalia. On the basis of GeoEye-1 imagery, semi-automatic object-based and manual image analysis approaches were applied, compared and evaluated regarding their analysis results (absolute numbers, population estimation, spatial pattern), statistical correlations and production time. Although even the results of the visual image interpretation vary considerably between the interpreters, there is a similar pattern resulting from all methods, which shows same tendencies for dense and sparse populated areas. The statistical analyses revealed that all approaches have problems in the more complex areas, whereas there is a higher variance in manual interpretations with increasing complexity. The application of advanced rule sets in an object-based environment allowed a more consistent feature extraction in the area under investigation that can be obtained at a fraction of the time compared to visual image interpretation if large areas have to be observed.

Object-Based Analysis and Fusion of Optical and SAR Satellite Data for Dwelling Detection in Refugee Camps

This study investigates the potential of very high spatial resolution (VHSR) optical WorldView-2 (WV-2) and single-polarized TerraSAR-X (TSX) synthetic aperture radar (SAR) satellite data for an automated detection of different dwelling types in a refugee camp by means of object-based image analysis (OBIA). First, the optical data and SAR data are analyzed independently, and then a fusion of both data sets is performed applying two different approaches: 1) an overlay operation-based procedure integrating the independent results of the optical- and SAR-based dwelling detection, and 2) a feature-based analysis approach taking advantage of the conjoint analysis of both data sets. The results of the single-sensor and the data fusion approaches are evaluated in detail on the basis of object-based and area-based accuracy assessments. Advantages and limitations of the analysis approaches are discussed. The accuracy rates reveal that the use of optical satellite data shows promising results regardless of the dwelling material, while the SAR data are suitable for the detection of metal sheet dwellings only. In complex camp areas, with closely spaced containers, the results of the independent analyses can be improved significantly by the proposed fusion approaches. The combination of SAR and optical data allows for the separation of contiguous dwellings in cases this was not possible by the optical sensor information

Earth observation-based multi-scale impact assessment of internally displaced person (IDP) camps on wood resources in Zalingei, Darfur

This study describes the development of a semi-automatic object-based image analysis approach for the detection and quantification of deforestation in Zalingei, Darfur, in consequence of the increasing concentration of refugees or internally displaced persons (IDPs) in the region. The classification workflow is based on a multi-scale approach, ranging from the analysis of high resolution SPOT-4 to very high resolution IKONOS and QuickBird satellite imagery between 2003 and 2008. The overall accuracy rates for the classification of the SPOT 4 data ranged from 92% up to 95%, while those for the QuickBird and IKONOS classification have shown values of 88 and 87%, respectively. The resulting trends in woody vegetation cover were compared with the development of the local population and the variability of precipitation. The results show that the strong increase in human population in the Zalingei IDP camps can be associated with considerable decrease in woody vegetation in the camp vicinity.

Temporäre Siedlungen: Wenn aus Flüchtlingslagern Städte werden

Fluchtlingslager sind immer nur als temporare Siedlungen geplant. Die Realitat zeigt jedoch oft ein anderes Bild. Viele Fluchtlingslager bestehen uber Jahrzehnte und entwickeln sich im Laufe der Zeit zu permanenten Siedlungen. Unter dem Einfluss eines hohen Bevolkerungsdrucks verandert sich dabei nicht nur die Gebaude- und Bevolkerungszahl, sondern auch die Siedlungs- und Infrastruktur. Hierbei sind oftmals deutliche Anzeichen stadtischer Entwicklung erkennbar. Der Entstehung von Fluchtlingslagern liegt ein geplanter Prozess zugrunde: In Sektoren und Blocken aufgestellte Unterkunfte dienen als Ausgangsbasis. In einem organischen Prozes werden nun vermehrt individuelle Behausungen errichtet. Entlang der Hauptwege entstehen verschachtelte enge Gassen mit Markten. Mit Hilfe der Fernerkundung lassen sich Informationen uber derartige Veranderungen ableiten und Erkenntnisse uber die Siedlungsstrukturen in Fluchtlingslagern, als ein Beispiel temporarer Siedlungen, gewinnen.

Towards a multi-scale approach for an Earth observation-based assessment of natural resource exploitation in conflict regions

Abstract The exploitation of resources, if not properly managed, can lead to spoiling natural habitats as well as to threatening people’s health, livelihoods and security. The paper discusses a multi-scale Earth observation-based approach to provide independent information related to exploitation activities of natural resources for countries which are experiencing armed conflict. The analyses are based on medium to very high spatial resolution optical satellite data. Object-based image analysis is used for information extraction at these different scales. On a subnational level, conflict-related land cover changes as an indication of potential hot spots for exploitation activities are classified. The regional assessment provides information about potential activity areas of resource exploitation, whereas on a local scale, a site-specific assessment of exploitation areas is performed. The study demonstrates the potential of remote sensing for supporting the monitoring and documentation of natural resource exploitation in conflict regions.