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Enhanced Support of OGC's Web Coverage Service (WCS) in MapServer 6.0
Stephan Meissl, EOX IT Services GmbH (S. Meissl, F. Schindler)
Frank Warmerdam, Independent
MapServer 6.0 is the first widely used web mapping software providing a WCS 2.0 server implementation. The new download standard WCS 2.0 was adopted by the Open Geospatial Consortium (OGC) in August 2010. WCS 2.0 support is included in the new version 6.0 of MapServer, among a long list of improvements, including also support of XML/POST protocol binding in WCS 1.1.
This presentation puts focus on technical aspects of the implementation and will include tips, tricks, and examples for the real world usage of WCS in MapServer focusing on the new version 2.0.
WCS 2.0 uses a coverage model which is based on GML and harmonized around OGC working groups thus allowing the usage of coverages interoperably and independently from a particular service. WCS 2.0 is defined as a modular, structured suite of specifications fitting into an extensible overall concept. The properties defined in the core (mainly consisting of coverage retrieval, sub-setting by trimming and slicing) must be offered by any conformant implementation. Extensions add optional further functionality like protocol bindings or format encodings.
The audience should not be afraid of snippets from Mapfiles, XMLs, XML Schemas, etc. as the presentation shows internals of the MapServer configuration and the WCS functionality. Based on real world examples from the Earth Observation domain the usage of the following functionalities is demonstrated: (i) configuration of coverages in MapServer via simple or tileindex layers, (ii) usage of output-format declarations and how they can be used with WCS, (iii) elements used/shown on service level in GetCapabilities responses and on coverage level in DescribeCoverage responses, and (iv) coverage retrieval via GetCoverage requests. The later highlights: (a) sub-setting in pixel or spatial coordinates, (b) requesting multipart/mixed responses including the GML coverage description, (c) usage of KVP and XML/POST protocol binding, (d) sub- setting of bands, (e) requesting reprojected or resized coverages using a specific interpolation.
Work on WCS 2.0 support has been partly funded by ESA in the frame of the HMA-FO project.
Stephan Meissl works in Austria, Europe as co-founder of EOX IT Services GmbH. He gained experience in various projects funded by the European Space Agency focusing on on-line data access to Earth Observation data. He is actively participating in OGC's Web Coverage Service (WCS) Standards Working Group. His Open Source involvement includes active contributions to OSGeo's MapServer project and initiating the EOxServer project. He graduated as Master of Science in the field of Mathematics in Computer Sciences from the Vienna University of Technology.
Frank Warmerdam has been a contract geospatial software developer focused on data access and interchange since 1998. He is the founder of the GDAL/OGR project, and contributing to projects such as MapServer, PROJ.4, OpenEV, libtiff and libgeotiff. He is a founding member and director of the Open Source Geospatial Foundation (OSGeo). He is a graduate of the University of Waterloo, with a honours BMath majoring in Computer Science.