Adding a new dimension to global urban observations: Inventory of human settlements pattern and urban morphology using VHR SAR data of the TanDEM-X mission

The German TanDEM-X mission has collected two global coverages of very high resolution synthetic aperture radar (SAR) X-band data with a spatial resolution of about three meters in the years 2011/2012 and 2012/2013. Such an extraordinary data set provides Earth observation data complementary to the existing global coverages with optical imagery. In this paper we present i) the technique implemented to identify and map human settlements in a so far unique spatial detail of ~12m, and ii) demonstrate the potential to characterize human settlements properties and patterns as well as the urban morphology (e.g., in terms of building height) using the worldwide data available from TanDEM-X mission. The basic approach towards the fully-automatic detection and delineation of built-up areas from TanDEM-X imagery, is presented by describing the corresponding operational processing environment - the Urban Footprint Processor (UFP) - and the resulting geo-information product - the Global Urban Footprint (GUF) mask. Along with this, we introduce a procedure that exploits the information provided by the GUF settlement mask to facilitate an effective spatial and structural characterization of human settlement forms and patterns from the local to the continental scale. Moreover, we also present a novel technique for estimating the building height within the human settlements delineated in the GUF by means of the digital elevation model (DEM) generated in the context of the TanDEM-X mission. The results of the study indicate the high potential of the developed geo-information products to support the analysis of urbanization patterns, the urban-rural continuum, peri-urbanization, spatio-temporal dynamics of settlement development as well as population estimation, vulnerability assessment and global change modeling.