Dear Ethan
I agree with Steve about ugrid and aggregation being important topics.
> 1. "UGRID"
The ugrid design is rather CF-compatible and it would be good if they could be
cemented together somehow. ugrid could be a proposed as a chapter of CF but it
doesn't have to be, of course. I suppose the advantage of doing so would be
that CF and ugrid development would subsequently remain compatible.
Could ugrid deal with this one of your agenda items:
> * Drafting a CF enhancement that would add support for complex data
> footprints (e.g., river segments and drainage basins)
I'm not sure what you have in mind but it sounds possibly related.
> 2. "Aggregation" -- CF structures to link multiple files into larger
> conceptual datasets. Time series aggregations, union aggregations
> (associated variables in separate files), and ensemble membership
> are the most obvious applications of this. Another important
> application is "tiled grids" (ref. the "gridspec" proposal).
There are various types of aggregation which should be distinguished, I think.
* Aggregation of variables. This is needed when one variable is split among
several files (often along the time axis) but it can also apply to variables in
the same file (for instance combining ensemble members or time series with the
same time coordinates - Steve's other examples). In general it means combining
several variables to make one variable, by concatenating one or more of their
axes. This can be done entirely using CF metadata and David Hassell and I wrote
a CF proposal for it
http://cf-trac.llnl.gov/trac/ticket/78 a long time ago,
which David has since implemented in cf-python software. I believe that this
approach is fine for CMIP6 purposes, for example.
* Aggregation of domains. By this I mean regarding domains which have their
own axes as part of a larger domain, like gridspec does. It's not aggregation
of variables in the same sense as above because the axes can't be concatenated.
It is similar to ugrid, though, and I think it would be good if an extension
to CF like ugrid could be developed for this.
* Aggregation of files. By this I mean regarding several files as one file
*without* associating or joining variables together, just putting them into
one container. This needs rules for dealing with collisions of identically
named variables, like NCO ncks has, or groups could be used, which are also on
Ethan's agenda.
> Harmonizing CF grid mapping with OGC CRS (coordinate reference
> systems), possibly with WKT
It should be possible to translate between CF and OGC CRS descriptions. Some
extensions to help with this are in
http://cf-trac.llnl.gov/trac/ticket/80,
which will be in CF 1.7, as will
http://cf-trac.llnl.gov/trac/ticket/69, which
allows WKT to be stored in a CF attribute. CF and OGC CRS have different views
of the data space, so I don't think we can expect to make them look the same,
but we should be able to define a mapping for all those concepts which are in
both.
Best wishes
Jonathan
----- Forwarded message from Ethan Davis <edavis at ucar.edu> -----
> Date: Sun, 27 Mar 2016 22:24:56 -0600
> From: Ethan Davis <edavis at ucar.edu>
> To: CF metadata <cf-metadata at cgd.ucar.edu>, netCDF SWG
> <netcdf.swg at lists.opengeospatial.org>
> Subject: [CF-metadata] Meeting invite: Advancing netCDF-CF, 24-26 May 2016,
> Boulder, CO, USA
>
> Hi all,
>
> As some of you have heard, we are holding a meeting to discuss current and
> future netCDF-CF efforts and directions. The meeting will be held on 24-26
> May 2016 in Boulder, CO, USA at the UCAR Center Green facility.
>
> This meeting is organized by the ?Advancing netCDF-CF for Geoscience?
> project [1] which has been funded by the US NSF EarthCube program. The
> project goals include several specific CF development efforts, both
> standards development and software prototyping. (We are just starting to
> spin-up community conversations around these specific goals for drafting CF
> extensions.) Another aspect of the funded project is community engagement
> including with the existing CF community, geoscience domains that have not
> been very involved in CF, and other standards bodies (e.g., OGC). These and
> other topics are on the current list of possible agenda items. Please let
> us know if you have other agenda items in mind.
>
> The current list of possible agenda items includes:
>
> - Investigate using features of the netCDF enhanced data model to
> improve/simplify the CF Discrete Sampling Geometries (which includes point,
> sounding, and trajectory data types)
> - Drafting a CF enhancement that would add support for complex data
> footprints (e.g., river segments and drainage basins)
> - Further develop the CFRadial proposal for representing Radar data
> - Adding features to better support satellite data
> - Adding CF support for hierarchical groups for organizing data and
> metadata
> - Enhancing CF to support Linked Data / semantic technology concepts
> - Harmonizing CF grid mapping with OGC CRS (coordinate reference
> systems), possibly with WKT
> - Adding CF support for attribute namespaces and the use of URI prefixes
> in attribute values
> - Improved support for dimensionless data variables, logarithmic scales,
> differences, etc.
>
> While we wish we could host all those interested in attending, given the
> available meeting space and the number of project participants, we are
> asking members of the CF community that are interested in attending to
> contact us directly and let us know which aspects of CF are of interest to
> you and your goals for the meeting. Please submit your expressions of
> interest by Monday, 4 April 2016. We plan to invite participants by Friday,
> 8 April 2016.
>
> Travel and other information will be on the meeting page [2] later this
> week.
>
> Also, for anyone attending EGU in Vienna in April, we will have a splinter
> meeting (SMP32) to discuss netCDF-CF. The splinter meeting will be held on
> Thursday, 21 April 2016 at 15:30 in room 2.96.
>
> Thank you,
>
> Meeting Organizers
>
> Ethan Davis, UCAR Unidata
> Charlie Zender, Univ of CA, Irvine
> David Arctur, Univ of TX, Austin
> Dave Santek, Univ of WI, Madison / SSEC
> Kevin O?Brien, Univ of WA/JISAO and NOAA/PMEL
> Aleksandar Jelenak, The HDF Group
> Mike Dixon, NCAR/EOL
>
> [1] http://www.nsf.gov/awardsearch/showAward?AWD_ID=1541031
>
> [2] http://www.unidata.ucar.edu/events/2016CFWorkshop/
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
----- End forwarded message -----
Received on Tue Mar 29 2016 - 06:43:46 BST
