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

Hi John,
Thanks for this clarification. I'm referring to curvilinear grids (2d) in
our case at the moment. And yep, again, this would be for GeoTIFFs; for
those geospatial folks (mostly in the GIS community) for whom a NetCDF is
undesirable. Here's an example map from our Google Maps-based viewer that
pulls a tiled image overlay directly from TDS using ncWMS (wave height
forecast over Oahu). If you click on the map, it provides a GeoTIFF URL. I
limit the GeoTIFF link to our regular gridded datasets, but was hoping to
(someday) expand this to the rest of our forecast models (curvilinear):

http://www.soest.hawaii.edu/hioos/map/index.html?b=21.042210,-158.815613,21.906100,-157.134705&t=h&o=bath:2:75:0,sfore:1:ft:d5m0.x5.524t1308196800

Thanks for listening,
John Maurer
Pacific Islands Ocean Observing System (PacIOOS)
University of Hawaii at Manoa

On Wed, Jun 15, 2011 at 5:00 PM, john caron <caron@xxxxxxxxxxxxxxxx> wrote:

>  some terms as far as i understand:
>
> regular grids:                    1d x, y coordinates evenly spaced. only
> ones WCS 1.0 allows
> irregularly spaced grids:  1d x,y, but dont have to be even, eg gaussian
> latitudes.
> curvilinear grids:                2d x,y but each section is a quadilateral
> and connected to its neighbor (implicit topology)
>
> CF allows both irregular and curvilinear grids. one could extend WCS to
> return netcdf/CF irregular and curvilinear grids, without regridding.
>
> unstructured grids: arbitrary meshes, explicit topology, no CF standard
> yet.
>
> John, why do you want WCS? To get geotiffs, or ??
>
> On 6/15/2011 7:25 PM, Ben Domenico 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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>>
>>
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