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ISRIC - World Soil Information, Wageningen University PO Box 353, 6700 AJ Wageningen, the Netherlands URL: http://www.isric.org E-mail: {tom.hengl; hannes.reuter}@wur.nl Global DEM-derivatives The idea of a global repository of DEM-derivatives is not new. USGS has been maintaining the global 1 km HYDRO1k (http://eros.usgs.gov ) --- a repository of DEM derivatives (elevation, WTI, slope, aspect, flow direction, flow accumulation, drainage basins and streams). San Diego Supercomputer Center hosts a project called "Open Topography" (http://opentopography.org/ ) that aims at serving high resolution (LiDAR) data and tools. Esri™ will build and host a collection of multiresolution DEM derivatives, starting with SRTM and analytic services against it, as well as higher resolution DEM derivatives for places where the data is freely available. The data will all be available for free on ArcGIS.com. On the other hand, it is difficult for a single investigator or even one group to undertake complex geomorphometry on a global scale --- instead, cooperative initiatives (such as the geomorphometry.org) are needed. An open database of DEM- derivatives We propose here initiation of open database of DEM derivatives (a geo- morphometric atlas) --- an international network of mirrored servers that will host the largest collection of DEM derived products including reference methods, software tools and standards. Such geo-database would support the development of knowledge libraries, as well as continued testing and comparison of geomorphometric methods by the scientific community (Kleiner, 2011). Proposed implementation The database needs to guarantee the following five criteria (Hengl & Reuter 2008): Precision --- It needs to provide the best estimates of surface measures and objects, derived from the most accurate and current data and al- gorithms. Multiscale --- Input DEM need to reside within a multi-scale GIS so that it can be available at various resolutions. Open structure --- Users should be able to modify and adjust spatial queries to tailor surface measures and objects to fit specific needs. Web access --- The system should provide a high performance cached map services and interactive analytic functions as web services (e.g. viewshed and watershed delineation). Quality --- the input (DEMs) and algorithms should be continually evaluated and improved and maintained to ensure their fitness for use (minimum artifacts). Conclusions Demand for DEMs and their derivatives, evident from many different disciplines and applications, will prompt ever higher expectations for rigor and force the global scientific community to commit to an ongoing review of data standards. The Global DEM-derivatives initiative is a platform for meeting these expectations. References: Hengl, T., Reuter, H.I. (eds) 2008. Geomorphometry: Concepts, Software, Applications. Developments in Soil Science, vol. 33, Elsevier, 772 pp. Kleiner, K., 2011. Data on demand. Nature Climate Change 1, 10–12. Iwahashi, J. and R. J. Pike, 2007. "Automated classifications of topography from DEMs by an unsupervised nested- means algorithm and a three-part geometric signature." Geomorphology 86(3-4): 409-440. An open database of DEM-derivatives of the World T. Hengl & H.I. Reuter Fig. 1: An example of a complete topographic model of the world at resolution of 1 km. For more info see: http://commons.wikimedia.org/wiki/File:Globedem.png Fig. 2: The landform classification following Iwahashi and Pike (2007). Relief classes which are classified using an unsupervised nested-means algorithms. Fig. 3: Conceptual design for a geomorphometric atlas: a user defines various parameters and then downloads the data. Processing and derivation of surface descriptors is done directly on the server. LSP/LSO = Land Surface Parameters/Objects. GEOMORPHOMETRIC ATLAS Spatial query Thematic properties - LSP/LSOs type - algorithms - pre-processing steps type date New data Spatial properties - coordinate system - spatial resolution - extent (boundaries) Function library LSPs / LSOs DEM *Activate functions matching the best with users’ request according to the organizer criteria WEB-INTERFACE Outputs
