GALEON Network

The GALEON OGCnetwork provides an intellectual commons for continued work on GALEON (Geo-interface to Atmosphere, Land, Earth, Ocean, NetCDF).  For the first year, GALEON existed as an OGC WCS Interoperability Experiment (IE) for implementing  and testing clients and servers for WCS gateways to netCDF datasets.

The objectives of GALEON Phase 2 include:

  1. Defining and Adopting a "WCS Profile" for CF-netCDF as a WCS encoding format
    Current Draft Outline WCS CF-netCDF Profile:
    http://www.unidata.ucar.edu/projects/THREDDS/GALEON/netCDFprofile-short.htm
  2. Expanding the set of WCS clients, servers, and datasets available for interoperability testing
    See the Pointers to Datasets page in the list below.
  3. Collaborating closely with the OGC GEOSS Services Network (GSN) and the GMLJP2 initiative.
  4. Developing OGC catalog services (CSW) to complement the WCS interface on GALEON servers.
    Starting CSW/THREDDS initiative at George Mason University.
    http://geobrain.laits.gmu.edu/csw/discovery/

Item 1, the CF-netCDF WCS profile, is the top priority and the target is to have it adopted at the June meeting of the OGC Technical Committee.

Background information on GALEON IE Phase 1 is available at:

The GALEON Wiki
GALEON Phase 1 Activity Plan

Comments

GALEON Description

The GALEON OGC Network will continue the Phase 2 work of the GALEON Interoperability Experiment.

The original GALEON (Geo-interface to Atmosphere, Land, Earth, Ocean, NetCDF) WCS Interoperability Experiment (IE) was set up to implement a geo-interface to netCDF datasets via the WCS 1.0 protocol specification. One specific approach implemented 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 leverages the widespread base of OPeNDAP servers that provide access to netCDF datasets and accompanying THREDDS servers providing ancillary information about the datasets. The IE investigated the feasibility of adapting data and metadata originating from OPeNDAP/THREDDS servers to the WCS specifications, thus bridging the gap between the atmospheric, oceanographic and GIS communities, by alleviating data interoperability issues.

The GALEON Phase 1 experiment has delivered 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). It is important to note that, while it is convenient to refer to these as 5D datasets, the 3 spatial dimensions and temporal dimensions are fundamentally different in that they are part of the domain whereas the multiple parameters are part of the range in the WCS data models and interface specifications.

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://my.unidata.ucar.edu/content/projects/THREDDS/OGC/WCS-THREDDS%20Gateway.htm.

The primary objectives of phase 1 IE have been to determine whether:

  1. a viable WCS getCapabilities geo-interface (gateway in earlier versions) can be built on existing THREDDS inventory catalog services

  2. the ncML-G data model is adequate for providing describeCoverage responses for netCDF datasets

  3. there are any solutions to the previously identified limitations to geoTIFF encoding format for representing from 5D netCDF files in such a way that the relationships among layers is preserved

  4. the proposed ncML-GML encoding format is a practical solution to serving 5D data from netCDF files, either embedded (ASCII or attached binary) or linked (OPeNDAP link or other URL)

  5. netCDF itself is a viable WCS binary encoding format

  6. existing WCS clients are able to access analyze and display 5D data from netCDF files

  7. 5D geospatial data sets can be served efficiently through standard database technology
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