galeon – nerc/cclrc experience

OGC Technical Committee

Huntsville, 2006-03-08

GALEON – NERC/CCLRC experience

Andrew Woolf ([email protected])e-Science Centre, CCLRC Rutherford Appleton Lab

Acknowledgments:Dominic Lowe (British Atmospheric Data Centre)

Jon Blower (NERC Environmental Systems Science Centre)Nathan Bindoff, Glenn Hyland, Jason Roberts, Ian Cummings

(Tasmanian Partnership for Advanced Computing)NERC DataGrid team



Recommendations

1. Consider CSML ‘Grid’ for irregular grid domains

<Grid srsName="urn:EPSG:geographicCRS:4979" srsDimension="3" dimension="2"> <gml:limits> <gml:GridEnvelope> <gml:low>0 7</gml:low> <gml:high>0 13</gml:high> </gml:GridEnvelope> </gml:limits> <gml:axisName>gridI</gml:axisName> <gml:axisName>gridJ</gml:axisName> <ordinate> <gridAxesSpanned>gridI gridJ</gridAxesSpanned> <sequenceRule order="+y+x">Linear</sequenceRule> <definesAxis xlink:href="#Lon"/> <axisValues> 1.00 1.10 1.20 1.30 1.40 1.45 1.50 1.55 1.60 1.50 1.45 1.35 1.30 1.20 1.10 1.18 1.27 1.36 1.46 1.48 1.57 1.65 1.71 1.62 1.58 1.50 1.48 1.40 ... </axisValues> </ordinate> ...</Grid>



Recommendations

2. Support New Work Item Proposal for ISO 19111 (Spatial referencing by coordinates - extension for parametric values), OGC 06-013

(some informative examples motivated by CF conventions)

Scope: “To define an extension of ISO 19111:2005 covering coordinate referencing systems where the coordinates are physical or material properties measured by parameters, such as pressure, rather than linear distance measurements. It defines a conceptual schema for the description of spatio-parametric coordinate reference systems. These parametric spatial reference systems will be modelled so that they may be associated with an ISO 19111 [horizontal] spatial coordinate reference system to form a compound spatio-parametric coordinate reference system.”



Recommendations

3. Rationalise binary encoding in GML (for coverage range and domain)

<gml:RectifiedGridCoverage gml:id="netcdf_ID0"> <gml:RectifiedGridDomain xlink:href="http://myserver/myfile.nc#temperature" xlink:role="http://netcdf/GMLOps/Grid/spatialDomain"/> <gml:rangeSet> <gml:File> <gml:rangeParameters> <gml:Quantity uom="degC"/> <fileReference>http://myserver/myfile.nc#temperature </fileReference> <fileStructure>Record Interleaved</fileStructure> <mimeType>application/x-netcdf</mimeType> </gml:rangeParameters> </gml:File> </gml:rangeSet></gml:RectifiedGridCoverage>



Recommendations

4. Add “CF-netCDF” to allowed formats• HDF netCDF• HDF-EOS CF-netCDF

5. BBOX clarification w.r.t. CRS• e.g. EPSG:4979 (lat, lon, height)

• BBOX=lat1,lon1,height1,lat2,lon2,height2, not• BBOX=minx,miny,maxx,maxy,minz,maxz



Recommendations

6. Harmonise WMS, WCS: BBOX and ELEVATION

• WCS 1.0.0:BBOX=minx,miny,maxx,maxy,minz,maxz

• WMS 1.3.0:BBOX=minx,miny,maxx,maxy&ELEVATION=minz/maxz/resz



Recommendations7. Eliminate mandatory WIDTH (RESX), HEIGHT (RESY),

DEPTH (RESZ)• to enable arbitrary slicing through four dimensions• e.g., Hovmüller (timeseries) of winds from 110-190E

BBOX=110,-45,190,-45,1000,1000&TIME=2004-08-01/2004-08-31 HEIGHT (RESY) and DEPTH (RESZ) irrelevant



Recommendations8. Clarify interpolation vs subsampling

• netCDF API:nc_get_vars_*(ncid,varid,start,count,stride,buf)

• OPeNDAP:http://opendapserver/dataset?var[start:stride:stop]

• WCS should support subsampling– behaviour of INTERPOLATION?

9. Conventions for exposing netCDF attributes in WCS metadata, e.g.:

• netCDF variable name WCS ‘CoverageOffering/name’ • CF ‘long_name’ WCS ‘CoverageOffering/label’• CF ‘standard_name’ WCS

‘CoverageOffering/rangeSet/RangeSet/label’



Recommendations

10.Clarify roles of ‘temporalDomain’ and ‘spatialDomain/EnvelopeWithTimePeriod’

• unclear whether ‘temporalDomain’ mandatory for time-dependant data

Experimental WCS (and full report) at: http://glue.badc.rl.ac.uk/cgi-bin/TPAC/WCS

galeon – nerc/cclrc experience

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