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Key Results from GALEON

Key Results from GALEON. John Caron Ben Dominico UCAR/Unidata. Background. Open GIS Consortium (OGC) Industry/government consortium for creating interoperable standards for GIS Commercial, not open source Web Coverage Service (WCS)

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Key Results from GALEON

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  1. Key Results from GALEON John Caron Ben Dominico UCAR/Unidata

  2. Background • Open GIS Consortium (OGC) • Industry/government consortium for creating interoperable standards for GIS • Commercial, not open source • Web Coverage Service (WCS) • Client-server protocol for “coverage” data (satellite data seems to be their main use case) • XML over HTTP / SOAP • Specification version 1.0 (1.1 almost ready) • GALEON: OGC “interoperability experiment” for WCS clients and servers

  3. GALEON Objectives • Determine suitability of WCS interface for serving model data to GIS community (4D vs 2D) • Examine possibility of extending WCS to add netCDF to current blessed encodings: • GeoTIFF (TIFF with geospatial tags) • HDF-EOS (HDF4 plus NASA metadata) • DTED (NIMA/DOD digital elevation) • NITF (NIMA/DOD images) • GML (OGC XML data encoding) • Experiment with GML (Geography Markup Language) dialects and netCDF files • Make recommendations to WCS 1.1 spec

  4. Active Participants • Unidata/UCAR (Ben Domenico, John Caron) • U of Florence and IMAA-CNR (Stefano Nativi, Lorenzo Bigagli) • International University Bremen (Peter Baumann) • George Mason University (Liping DI, Wenli Yang) • CadCorp (Martin Daly, Frank Warmerdam (GDAL)) • Research Systems International UK Ltd (David Burridge, Norman Barker) (IDL) • NCDC, National Climatic Data Center (Glenn Rutledge, Dan Swank) • NERC Natural Environment Research Council/British Atmospheric Data Center (Dominic Lowe, Andrew Woolf) • Washington University St. Louis (Stefan Falke, Rudolf B. Husar) • Providing Specialized Expertise • Interactive Instruments (Clemens Portele) • NASA Geospatial Interoperability Office (John Evans)

  5. TDS GALEON Development • Process WCS GET requests (not SOAP) • Generate WCS XML documents • Map bounding boxes to index ranges • No regridding, no reprojection, want “raw” data • Create GeoTIFF images • Greyscale: min/max -> 1..255 • DataSample: Floating point (optional for readers) • No standards for missing data, time/vertical • Only implemented a few projections • Create subsetted netCDF/CF files • OPeNDAP WCS service http://motherlode.ucar.edu:8080/thredds/wcs?dataset=dodsURL

  6. NERC DataGrid Development • Created prototype WCS server (with TPAC) • Reads from various “backend providers” • Currently OPeNDAP • DataExtractor tool (NDG), GADS (Univ Reading), CSML (NDG) • Serves subsetted NetCDF/CF • Recommendations to clarify WCS • Investigate CSML as potential format, referencing netCDF through xlink or gml:File.

  7. Other WCS/netCDF Servers • Univ Florence (Nativi et al) • Also experiment with NcML-GML • Intl Univ Bremen (Baumann et al) • Import netCDF data into PostgreSQL database • Aggregate multiple files into a single database object • Rasdaman maps raster data to relational tuples, SQL variant queries. • Wash Univ St Louis (Husar et al) • Also tried to serve collection of irregularly located points • George Mason University (Liping DI et al)

  8. WCS/NetCDF clients • DataFed (Wash Univ St Louis) • George Mason University • SIS/GDAL, CadCorp (Martin Daly, Frank Warmerdam (GDAL)) • IDL, Research Systems International • Non-WCS: • ESRI (local NetCDF/CF files) ArcGIS 9.2

  9. Accomplishments • Recommendation for NetCDF as a WCS encoding (1.0) • Recommendations for changes to WCS 1.1 specification • Peter Baumann • Andrew Wolfe • Stefano Nativi • Develop netCDF “application profile” (1.1) • Investigation of GML applications profiles for explicit netCDF semantics (ncML-GML, CSML)

  10. Plans for Phase 2 • For continued experimentation with WCS implementation, use GALEON OGCnetwork • Additional client & implementations • New datasets • For WCS and GML specifications, continue as OGC GALEON Interoperability Experiment • Collaborate closely with: • OGC GEOSS Services Network (GSN) • GMLJP2 (GML JPEG2000)

  11. CF-netCDF WCS 1.1 Profile • Brief Description • Documentation • Standard names • Units • Coordinate types • Coordinate systems • Grid mappings • Time coordinate(s) • Code for Implementing netCDF Interface • Support • CF-netCDF and Coverage (ISO 19123) Data Model Mapping • Limitations • Compliance Testing

  12. Changes Proposed in WCS 1.1 • WCS encoding “profiles” instead of fixed list of encoding formats • Multiple “variables” or “parameters” or “fields” in a coverage (e.g., pressure, temperature, etc.) • Coverages with 3 spatial dimensions • Coverages with multiple time dimensions (e.g. forecast time in model output) • Non-spatial “height” dimension, (e.g., atmospheric pressure, ocean density) • Irregularly-spaced grids • Are collections of point observations and trajectories coverages or features?

  13. Summary • A handful of clients and servers have demonstrated feasibility • Commercial vendors are actively participating (RSI, ESRI, CADCORP) • GEOSS demonstrations involve WMS clients getting data from GALEON WCS servers • Finished netCDF profile is key; other profiles are needed (e.g., OPeNDAP, HDF-EOS, GeoTIFF) • Most WCS limitations are being addressed in 1.1 • With proposed changes, WCS should be viable for model datasets

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