Key Results from GALEON

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 -gt 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.edu8080/thredds/wcs?datase
  tdodsURL

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 gmlFile.

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