Urban remote sensing How can earth observation support the sustainable development of urban environments

Cities are centres of economy, policy, society and culture and more than half of the world’s population already lives in metropolitan areas. In the last decades the world has faced a constantly accelerating growth of urban areas - a development which is closely related to a tremendous increase of the urban population. In 2007 the amount of urban residents has outnumbered the rural population for the first time in history and by the year 2030 already two-thirds of the world’s population is expected to live in cities (UNPP, 2008). Hence, urban and peri-urban environments show one of the highest dynamics in the context of global land use transformations. The constant urbanization and the rapid changes in urban environments involve considerable challenges with respect to the observation, analysis and understanding of the complex processes affecting and forming metropolitan areas. As a consequence, effective and sustainable urban management increasingly demands innovative concepts and techniques to obtain up-to-date and area-wide information on the characteristics and development of the urban system – regionally as well as globally. Currently, most of this information is collected by means of statistics, surveys and mapping or digitizing from aerial imagery. However, in consideration of stastistical information these approaches often show a comparably coarse spatial and temporal resolution while surveying and mapping is time consuming and cost-intensive - properties which significantly restrict periodic updates and regional, national or even global analyses. Space- and airborne earth observation (EO) has become a promising tool to provide updated geoinformation on various aspects of built-up areas in manifold spatio-temporal dimensions (Bauer et al., 2004; Heiden et al. (2003); Henderson & Xia, 1998; Herold et al., 2003; Ji et al., 2006; Masek et al., 2000). Remotely sensed images represent an independent data source from which various layers of information can be derived area-wide, with a flexible repetition rate and in various scales ranging from spatially detailed analysis on single-building or building block level to global studies on continental scale. In combination with widely automated methods of data processing and image analysis, urban remote sensing provides multiple options to support decision makers such as resource managers, planners, environmentalists, economists, ecologists and politicians with accurate and up-to-date geoinformation. This paper introduces selected geo-information products derived from multisensoral remote sensing data. The products and the underlying remote sensing techniques were developed in the context of a joint research co-operation for urban applications between the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) and the Department of Remote Sensing at the University of