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Ben Domenico
Last modified:
September 9, 2005
The Open Geospatial Consortium (OGC) GALEON (Geo-interface for Atmosphere, Land, Earth, and Ocean netCDF) WCS Interoperability Experiment (IE) will implement a geo-interface to netCDF datasets via the WCS (Web Coverage Service) 1.0 protocol specification. It will implement the WCS as a layer above a set of client/server and catalog protocols already widely in use in the atmospheric and oceanographic sciences communities. In particular, it will leverage the widespread base of OPeNDAP servers that provide access to netCDF datasets and accompanying THREDDS servers providing ancillary information about the datasets.
The IE will investigate the feasibility of adapting data and metadata originating from OPeNDAP/THREDDS servers to the WCS specifications, in so contributing to bridge the gap between the atmospheric, oceanographic and GIS communities, by alleviating data interoperability issues. The initial experiments will deliver collections of numerical forecast model output which consist of what are sometime referred to as five dimensional or 5D grids (multiple parameters (e.g., temperature, pressure, relative humidity) varying in three spatial dimensions with two time coordinates (model run time and forecast time).
Since the initial discussions of GALEON at the New York meeting of the OGC Technical Committee in January, what has evolved is a combination of the formal OGC GALEON Interoperability Experiment along with several specific implementation projects. The formal OGC IE has to be conducted by OGC members, but the implementations can involve additional organizations. Thus, for example, the WCS gateway to underlying OPeNDAP/THREDDS/netCDF technology may involve organizations that are not part of the OGC IE but will play an active role in testing the implementation in real world settings. Likewise the component of the experiment relating to WCS implmentations via database technology may also involve groups that are not part of the formal OGC experiment.
Schematic of WCS Gateway to netCDF
This IE can be seen as a step in the direction of interoperability with data systems already in existence in the oceanographic and atmospheric sciences. These technologies include netCDF, OPeNDAP, ADDE, and THREDDS. An outline of the integration path is given in:
http://www.unidata.ucar.edu/projects/THREDDS/OGC/WCS-THREDDS%20Gateway.htm.
*Initiating institutions
The project has been formally underway less than a month, but considerable progress has been made already with several clients interacting with datasets on the Unidata WCS server (based on THREDDS Data Server technology) and the GMU netCDF server which was developed independently but also incorporates some to the TDS code. In addition, considerable work has been done at the University of Florence encoding netCDF semantics and, in some cases, netCDF data into various XML dialects based on the netCDF Markup Language (NcML).
More information about ncML, the ncML-G data model and the ncML-GML encoding are given in:
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