The Global Urban Footprint: Generating a Worldwide Settlement Mask from Data of the TanDEM-X Mission

Abstract

The German TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) mission collects two global data sets of very high resolution (VHR) synthetic aperture radar (SAR) images with a geometric resolution of three meters in the years 2011/2012 and 2012/2013. Such imagery provides a unique information source for the delineation of built-up areas in a spatial detail that could not be addressed with globally available data sets so far. This paper presents a fully-automatic processing system for the identification and delineation of built-up areas worldwide based on the SAR data provided by the TerraSAR-X and TanDEM-X mission. The proposed Urban Footprint Processor (UFP) includes three main processing stages dedicated to: i) the extraction of texture information suitable for highlighting regions characterized by highly structured and heterogeneous built-up areas; ii) the generation of a binary settlement layer (built-up, non-built-up) based on an unsupervised classification scheme accounting for both the original backscattering amplitude and the extracted texture; and iii) a final post-editing and mosaicking aimed at providing the final Urban Footprint (UF) product for arbitrary geographical regions. The accuracy of UF mosaics provided by the UFP has been assessed and the first results stress the high potential of the TerraSAR-X/TanDEM-X data and the proposed UFP, respectively, to provide accurate and spatially detailed geo-data for an improved mapping of human settlements worldwide.