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OGC GALEON (Geo-interface for Air, Land, Ocean NetCDF)

Phase 1 Status and Phase 2 Plans

Ben Domenico*, Unidata UCARGlenn Rutledge*, NCDC

For AGU Joint Assembly, May 2006

*Work sponsored in part by NSF and NOAA

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Outline

• Background

• Phase 1 Accomplishments,

• Phase 2 Directions

• WCS Implications

• Observations(Many slides just for future reference)

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Disparate Data Models:Different Ways of Thinking about Data

• To the GIS (solid earth and societal impacts) community, the world is:– A collection of static featuresfeatures (e.g., roads, lakes, plots of land)

with geographic footprints on the Earth (surface).– The featuresfeatures are discrete objectsdiscrete objects with attributes which can be

stored and manipulated conveniently in a database.database.

• To the Fluid Earth Sciences (FES -- atmosphere and oceans) communities, the world is:– A set of parametersparameters (e.g., pressure, temperature, wind speed)

which vary as continuous functionscontinuous functions in 3-dimensional space and time.

– The behavior of the parametersparameters in space and time is governed by a set of equations.equations.

– Data are simply discrete points in the mathematical function space.

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Traditional GIS view

Attributes in DBMS

tables

Features as points,

lines, polygons

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Typical NetCDF Visualization

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Taking Advantage of Web Services for Data System Interoperability

GIS ClientGIS Client Applications Applications

FES ClientFES Client Applications Applications

OpenGIS Protocols:WMS, WFS, WCS

OGC or proprietary GIS

protocols

OGC or OPeNDAPADDE. FTP…

protocols

GIS ServerGIS Server

GIS ServersGIS ServersDemographic, infrastructure, Demographic, infrastructure,

societal impacts, … societal impacts, … datasetsdatasets

THREDDS ServerTHREDDS ServerFES ServersFES Servers

Satellite, radar, Satellite, radar, forecast model output, … forecast model output, …

datasetsdatasets

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GALEON Objectives• Use standardized web service between GIS and

atmospheric/oceanographic clients and servers• Determine suitability of WCS (Web Coverage

Service) interface for serving traditional FES datasets to GIS community

• Implement WCS gateway(s) to existing FES client/server community, based on:– *netCDF (network Common Data Form),– OPeNDAP (Open Project for Networked Data Access

Protocol)– THREDDS (THematic Real-time Environmental

Distributed Data Services)

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NetCDF/OPeNDAP NetCDF/OPeNDAP data serverdata server

WCS Client

…

THREDDS THREDDS catalogs catalogs

enhanced with enhanced with NcML-GMLNcML-GML

WCS capabilities

THREDDS interface

WCS description

THREDDS interface

OPeNDAP

NetCDF dataset

NetCDF

OPeNDAP

GMLgenerator

geoTIFFgenerator

WCS coverage

netCDFgeoTIFF

NcMLGMLgetCoverage

getCapabilities

describeCoverage

THREDDS enhanced catalog generation tools

THREDDS catalogsNcML-G metadata

netCDF objects

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Tasks

• Find or implement WCS clients and servers for netCDF datasets

• Test WCS clients with WCS gateway servers• Examine possibility and implications of

extending WCS to include netCDF binary encoding

• Experiment with GML (Geography Markup Language) dialects for expressing Earth Science data model embodied in netCDF files

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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)• Research Systems International UK Ltd (David Burridge, Norman

Barker)• 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)

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Planning to Participate

• Texas A&M University (Gerry Creager)• University of Alabama Huntsville (Mike Botts) • Jet Propulsion Laboratory (Rob Raskin) • University of Applied Sciences (Ralf Denzer) • ESRI, Inc (Simon Evans, Steve Kopp)• CEOP (Ben Burford), Coordinated Enhanced Observing Period of

the Committee on Earth Observation Satellites (CEOS)• US EPA has expressed interest in servicing air quality data via a

GALEON test site• PFEL (Roy Mendelssohn)

Pacific Fisheries Environmental Laboratory

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Accomplishments

• Interoperability experiments with WCS client and server implementations at numerous sites (status reports on GALEON wiki and OGC portal)

• Several recommendations for changes to WCS specification (formal documents on OGC portal)

• Initiatives underway for GML applications profiles for explicit netCDF semantics (ncML-GML, CSML)

• Dialog initiated with GMLJP2 group to determine applicability to netCDF datasets

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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)

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OGC GEOSS Services Network (GSN)GALEON Contributions

• For OGC GEOSS demonstrations in Beijing and at IGARRS in Denver

• Data served via WCS at Unidata, NCDC, Washington U. in St. Louis, George Mason University

• Web client access via WMS on web sites at U of Florence, Washington U. St. Louis

• Thick Client access via RSI/UK, U of Florence, George Mason U. tools

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Primary OGC Interface Issues• NetCDF as a sixth WCS encoding format OR

• Develop netCDF application profile Develop netCDF application profile ANDAND

• Do away with fixed list of encoding formats Do away with fixed list of encoding formats (geoTIFF, HDF-EOS, NITF, DTED, GML)(geoTIFF, HDF-EOS, NITF, DTED, GML)

• Develop WCS application profile for netCDF• Augment WCS specification• Develop GML application schemas for netCDF

semantics (ncML-GML, CSML, GMLJP2?)

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CF-netCDF WCS 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

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netCDF – Coverage Mapping (S. Nativi)

Explicit mediation needed between netCDF hyperspatial data and

WCS coverage models

netCDF dataset WCS coverage

N independent dimensions (i.e. axes) 2, 3, 4 coverage domain dimensions

Set of scalar variables Coverage range-set of values

(t, z, y, x) variable shape (x, y, z, t) domain shape

Implicit geo-location metadata Explicit geo-location metadata

Grid geometry irregularly spaced Grid geometry regularly spaced

etc. etc.

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netCDF-relatedChanges 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?

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Observations and Assessment• A handful of clients and servers have demonstrated

feasibility• Commercial vendors are actively participating (RSI,

ESRI, others)• 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

FES datasets

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References

• GALEON Wikihttp://galeon-wcs.jot.com/WikiHome

• OGC portal GALEON areahttp://portal.opengeospatial.org/index.php?m=projects&a=view&project_id=173

• OGCnetworkhttp://www.ogcnetwork.net/?q=networks

• Draft CF-netCDF WCS Encoding Profilehttp://www.unidata.ucar.edu/projects/THREDDS/GALEON/netCDFprofile-short.htm