On Wed, Mar 30, 2016 at 1:09 PM, Ethan Davis <edavis at ucar.edu> wrote:
> Yes, though I'm not that familiar with the details of UGRID, it does (now
> that you mention it) seem related in some ways to the river/basin topic.
>
well, maybe -- but while UGRIDs are "unstructured", there is SOME structure
to them -- i.e. they are usually made up of cells with the same number of
sides (triangles, quads, etc), or at least a small number (six or less).
And the UGRID data structure does assume this.
> I've been thinking of the river/basin
>
Rivers can be a 1-d "mesh" which there is support in UGRID for, but I think
of basins as being arbitrary often high order polygons.
Is there any standard for supporting polygons (i.e. what you might put in
shape files) in netcdf?
-Chris
> On Tue, Mar 29, 2016 at 6:43 AM, Jonathan Gregory <
> j.m.gregory at reading.ac.uk> wrote:
>
>> 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 -----
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>
>
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>
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
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