1. University of Cologne, Institute of Geography, GIS and RS Group, Albertus-Magnus-Platz, Köln 50923, Germany
2. University of Cologne, Institute of Geography, GIS and RS Group, Albertus-Magnus-Platz, Köln 50923, GermanybUniversity of Bonn, Center of Remote Sensing of Land Surfaces (ZFL), Walter-Flex-Straße 3, Bonn 53113, Germany