Re: [thredds] future TDS WCS support for irregular/curvilinear grids?

Hi Jon,
Thanks for the follow-up. It would be great (in my opinion) to get this
nearest-neighbour scheme folded into the TDS WCS for GeoTIFF output. I was
hoping something like that could be possible with some (hopefully relatively
painless?) re-use of your code. I also completely concur with your aside
about GIS users.
Cheers
John

ncWMS (and hence THREDDS-WMS) uses a simple nearest-neighbour scheme for
> regridding, which seems fine for producing images (at least, no-one has ever
> complained!) but may not be appropriate for serving data, depending on what
> you want to do.****
>
> ** **
>
> However, if THREDDS wants a means to serve resampled data through WCS, the
> WMS libraries should make this pretty easy to implement.  But the user must
> be aware that the data have been processed at the server side.*****
>
> ** **
>
> We would also need to implement GeoTIFF output for your needs… probably
> there is code out there to do this already.****
>
> ** **
>
> Hope this helps,****
>
> Jon****
>
> ** **
>
> [* Aside: in my view, the WCS interface is most useful for GIS users, who
> are much less likely to care about how data are regridded than scientific
> users; scientific users can use OPeNDAP to get the “raw” data of course.
> Perhaps in most cases, GIS users just need a “WMS for data” rather than a
> full-fledged scientific data server.  But I don’t know how THREDDS-WCS is
> used in the wild.]****
>
> ** **
>
> ** **
>
> *From:* John Maurer [mailto:jmaurer@xxxxxxxxxx]
> *Sent:* 16 June 2011 02:47
> *To:* THREDDS Users
> *Cc:* Jon Blower
>
> *Subject:* Re: [thredds] future TDS WCS support for irregular/curvilinear
> grids?****
>
> ** **
>
> Thanks, Ben! Sounds good! Glad to hear things are progressing along these
> lines. Sounds like it could be quite some time, though, before irregular
> grids are formally adopted by the international standards community and
> trickle down to all of us here in TDS-land. This is why I was hoping Unidata
> could maybe short circuit this process by regridding the data onto a regular
> grid via the TDS backend and then serving it out through WCS (1.0) that way.
> But that is maybe asking (way) too much. Again, ncWMS is presumably doing
> something similar to provide WMS for irregular grids (see attached image)?
> Or is the WMS spec ahead of WCS in terms of its adoption of irregular grids?
> Perhaps Jon Blower could elucidate (cc'd)...
>
>
> [image: sst_roms_curvilinear.png]
>
> Cheers,
> John Maurer****
>
>  On Wed, Jun 15, 2011 at 3:25 PM, Ben Domenico <Ben@xxxxxxxxxxxxxxxx>
> wrote:****
>
> Hi John et al.,****
>
> ** **
>
> I am currently at the OGC Technical Committee meetings so your note is
> quite timely.  My concept of how this sort of capability might be worked
> into the standards -- from the netCDF point of view anyway -- is via the CF
> conventions.    We are currently working on a CF extension for the OGC
> netCDF core standard.  At the same time we are working on a CF-netCDF
> encoding standard for WCS 2.0.  But my understanding is that
> irregular/curvilinear grids are not formally adopted yet as part of the CF
> conventions.  When these grids officially become part of CF, we can then do
> a revised extension to CF-netCDF and to WCS.****
>
> ** **
>
> Please correct me if I'm wrong about the status of irregular/curvilinear
> grids in CF.  If you have suggestions for better ways to accomplish this,
> let me know.   But for now this is the general outline of the plan for
> getting this into the formal standards world.  ****
>
> ** **
>
> For what it's worth.****
>
> -- Ben****
>
> ** **
>
> On Wed, Jun 15, 2011 at 6:23 PM, John Maurer <jmaurer@xxxxxxxxxx> wrote:**
> **
>
> Thanks for the explanation, Ethan. If TDS could handle the regridding
> itself, then it could work. I assume this is what's happening on the backend
> via TDS/ncWMS for GetMap requests since the WMS spec doesn't handle
> irregular/curvilinear grids either (right?). I was hoping a future
> enhancement could someday do the same for TDS WCS. Something for the
> suggestion box.
> Cheers,
> John****
>
> ** **
>
> On Wed, Jun 15, 2011 at 2:17 PM, Ethan Davis <edavis@xxxxxxxxxxxxxxxx>
> wrote:****
>
> Hi John,
>
> TDS currently only supports WCS 1.0.0. The WCS 1.0.0 specification
> itself does not support requesting or returning irregular/curvilinear
> grids. I believe the same is true for WCS 1.1.0.
>
> I don't belive this is necessarily the case for WCS 2.0. However, the
> 2.0 specification is written in the new core/extensions paradigm and I
> don't believe the extensions necessary to request or return
> irregular/curvilinear grids are yet written.
>
> The TDS WCS implementation does not currently support regridding data.
> So, currently one gets the data from the WCS in the same projection in
> which the data is stored. The combination means the TDS WCS can only
> serve regularly gridded data.
>
> Ethan****
>
>
> On 6/15/2011 5:31 PM, John Maurer wrote:
> > Hi All,
> > We now use the WCS service through TDS to serve GeoTIFF files to users.
> > Since it only works for regular grids, I was wondering if TDS could be
> > enhanced in the future to support irregular/curvilinear grids via WCS?
> > TDS/ncWMS already handles curvilinear grids via WMS, so I was hoping the
> > same sort of intervening magic could be applied for TDS' WCS service?
> > Thoughts?
> > Thanks for listening!,
> > John Maurer
> > Pacific Islands Ocean Observing System (PacIOOS)
> > University of Hawaii at Manoa****
>
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