Grids and Beyond: netCDF-CF and ISO/OGC Features and Coverages Ethan Davis, John Caron, Ben Domenico...
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Transcript of Grids and Beyond: netCDF-CF and ISO/OGC Features and Coverages Ethan Davis, John Caron, Ben Domenico...
Grids and Beyond: netCDF-CF and ISO/OGC Features and Coverages
Ethan Davis, John Caron, Ben DomenicoUCAR/Unidata
AMS IIPS, 23 January 2008
Non-gridded Data
Modeling Scientific Datatypes• Point, Station, Profile, Trajectory, Grid, …
– Unidata CDM– CSML– OGC O&M
• Why– Categorize by structure/connectedness– Consider specialized queries in space and time– Help with encoding (netCDF, CF)
• How– ISO Coverage model (ISO 19123)
Why ISO Coverages?
• Very general model for representing fields that vary over a spatial domain (e.g., temperature)
• Promote interoperability– Well accepted standard
• OGC WCS data access protocol is based on the ISO Coverages
OGC Web Coverage Service
• Specification for accessing subsets of gridded data.
• Currently restricted to gridded data and further to regularly spaced gridded data.
• Not due to limitations of the ISO coverage model.
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries
ISO Coverage and Feature
• ISO coverage is an extension of the ISO feature concept
• Feature is an abstract representation of a real-world phenomena.
• A bit more concretely …
ISO Coverage and Feature
Simple Feature: generally an object with some spatial extent or geometry and a set of attributes. E.g., a lake has a shoreline and a name
ISO Coverage and Feature
Coverage: a spatial domain and the set of parameters that vary over that domain. E.g., a lake has a depth at every point.
ISO Coverage and Feature Different views of the same data
Collection of point features
Time series coverage
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries
WCS Response EncodingnetCDF-CF
• netCDF-CF good for gridded data– Including irregularly spaced grids– Non-gridded not as fully specified
• Current efforts to extend CF– Unidata Point Observation Convention– Coordinate Reference System (CRS)
proposal– Unstructured grids
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries
WCS Queries
• Current WCS queries:– Lat/lon/Z (X/Y/Z) bounding box– Time range– Parameter selection (subsettable if there is a
parameter dimension, e.g., spectral bands)• What other queries would be useful with
non-gridded data
WCS Queries
Specialized queries for a datatype..
Example: Station collection
Request:bbox=10,-105,50,-80
WCS Queries
Specialized queries for a datatype..
Example: Station collection
WCS Queries
Specialized queries for a datatype..
Example: Station collection
Request:Stn=71815,71867,72214
WCS Queries
Extract one datatype from another datatype.
Example: Time series from a grid at a given point.
Request:datatype=timeseries&pnt=30,-90
WCS Queries
Extract one datatype from another datatype.
Example: Vertical profile from a 3-D grid at a given point.
Request:datatype=profile&pnt=30,-90
WCS Queries
Extract one datatype from another datatype.
Example: Trajectory data from a 4-D grid, given an xyzt curve.
Request:datatype=trajectory& ???
WCS Queries
Extract one datatype from another datatype.
Example: Trajectory data from a 4-D grid, given an xyzt curve.
Request:datatype=trajectory &featureURI=flightTrack.xml
WCS Queries
Extract one datatype from another datatype.
Example: Station data from a grid.
Request:datatype=station& ???
WCS Queries
Extract one datatype from another datatype.
Example: Station data from a grid.
Request:datatype=station &featureURI=stnList.xml
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries
WCS and Non-gridded Data
• Possible?• What is needed
– Model datatypes using ISO Coverage model– Translate the model to XML/GML– WCS response encodings (netCDF-CF)– WCS queries– Evolve the WCS specification
Thanks
• BADC (Andrew Woolf, Bryan Lawrence)• UK Met Office (Jeremy Tandy, Bruce Wright)• Univ of Florence (Stefano Nativi)• CSIRO (Simon Cox)• OGC• GALEON
Contacts
Ethan Davis, [email protected]