1. Grids and Beyond: netCDF-CF and ISO/OGC Features and Coverages Ethan Davis, John Caron, Ben Domenico UCAR/Unidata AMS IIPS, 23 January 2008

2. Non-gridded Data

3. 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)

4. 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

5. 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.

6. 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

7. 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 …

8. 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

9. 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.

10. ISO Coverage and Feature Different views of the same data Collection of point features Time series coverage

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. WCS Queries Specialized queries for a datatype.. Example: Station collection Request: bbox=10,-105,50,-80

18. WCS Queries Specialized queries for a datatype.. Example: Station collection

19. WCS Queries Specialized queries for a datatype.. Example: Station collection Request: Stn=71815,71867,72214

20. WCS Queries Extract one datatype from another datatype. Example: Time series from a grid at a given point. Request: datatype=timeseries&pnt=30,-90

21. 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

22. WCS Queries Extract one datatype from another datatype. Example: Trajectory data from a 4-D grid, given an xyzt curve. Request: datatype=trajectory& ???

23. 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

24. WCS Queries Extract one datatype from another datatype. Example: Station data from a grid. Request: datatype=station& ???

25. WCS Queries Extract one datatype from another datatype. Example: Station data from a grid. Request: datatype=station &featureURI=stnList.xml

26. 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

27. 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

28. Thanks BADC (Andrew Woolf, Bryan Lawrence) UK Met Office (Jeremy Tandy, Bruce Wright) Univ of Florence (Stefano Nativi) CSIRO (Simon Cox) OGC GALEON

29. Contacts Ethan Davis, edavis@unidata.ucar.edu