Large-Area Characterization of Urban Morphology-Mapping of Built-Up Height and Density Using TanDEM-X and Sentinel-2 Data

In this paper, we establish a novel multistep procedure for morphologic characterization of built environments in terms of built-up height and density. We rely on elevation measurements from the TanDEM-X mission (TDM) and multispectral Sentinel-2 imagery. These earth observation systems feature a notable tradeoff between a fairly high spatial resolution and large-area coverage and, thus, allow for spatially continuous analysis of built environments around the globe. To this purpose, we follow an automated workflow that foresees the distinction of built-up and non-built-up areas by relying on the so-called Global Urban Footprint processor. This information is deployed within a tailored filtering procedure for the TDM digital surface model data to extract elevation information for built-up areas. Subsequently, the intra-urban land cover is mapped under consideration of Sentinel-2 imagery and serves as basis to compute built-up heights and densities. These two measures are finally combined for a morphologic characterization of the built environment on an ordinal scale of measurement. Empirical validation efforts are provided based on comparative analysis with respect to more than 3.2 million individual building geometries and affiliated height measurements from cadastral data sources. The datasets cover the settlement areas of the capital cities and other major cities in Germany, England, and the Netherlands. The experimental results underline the capability for a morphologic characterization of built environments with viable accuracies.