Grids and Beyond: netCDF-CF and ISO/OGC Features and Coverages Ethan Davis, John Caron, Ben Domenico UCAR/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 Encoding netCDF-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,