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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

Key Results from GALEON

John Caron

Ben Dominico

UCAR/Unidata

background
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
galeon objectives
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
active participants
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)
tds galeon development
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

nerc datagrid development
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.
other wcs netcdf servers
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)
wcs netcdf clients
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
accomplishments
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)
plans for phase 2
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)
cf netcdf wcs 1 1 profile
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
changes proposed in wcs 1 1
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?
summary
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