Minutes for the MetOcean DWG Teleconference on 30th January 2012, 16:00 - 17.04 UTC
Stephan Siemen (ECMWF)
Jeff de la Beaujardière (NOAA)
Ben Domenico (UNIDATA)
Frederic Guillaud (Météo-France)
Marie-Françoise Voidrot (Météo-France)
Topics in the order of discussion:
Status of the works :
The use of the TIME Dimension is has been defined and validated in teleconfs and in a TC. It is stable as defined at : http://external.opengis.org/twiki_public/MetOceanDWG/MetOceanWMSBP20111212
The proposal for a dimension ANALYSIS TIME has been discussed in teleconfs and should be presented for validation at the Austin TC. (see current proposal at : http://external.opengis.org/twiki_public/MetOceanDWG/MetOceanWMSBP20111212
To answer the needs in term of time of Climatological products identified in http://external.opengis.org/twiki_public/MetOceanDWG/MetOceanWMSBP20111212
it was proposed to "put the time semantics to define the product into the name of the layer" ( 9th of January) but at the following teleconf (16th January) it was "suggested that it would be better if there would be no internal data structure in the Name element, but a "Keyword" element with a specific "vocabulary" attribute used for this information"
As this subject has to be discussed at an INSPIRE expert meeting next week, we put the subject in standby waitng for some feedbacks.
The next point was to try to stabilise the needs in term of Vertical CRSs to provide Andrew Woolf with a clear input. Andrew will then check how it fits into ISO 19111-2 spec or suggest some ways to go forward.
Jeff reminds that the ELEVATION can be defined with an EPSG reference
Based on some infos provided by Martin Desruisseaux : "This concept of Sample Dimension comes from OGC01-004 "Grid Coverage implementaion specification". This specificaiton is now "deprecated documents" section of OGC. However it still has usefull information which are not directly found in ISO 19123. The concept of "Sample Dimension" as defined in OGC 01-004 is close to the concept of "Range" in ISO 19123, however OGC 01-004 was defined in a more "practical" perspective. Note that this concept of Sample Dimension has been recycled and now appears in the current draft of ISO 19115:2011 (or at least one of the drafts not yet officially released) as a super-type of MD_Band.
From ISO 19115 point of view, a "band" is a "sample dimension" specialized to measurement in the electromagnetic spectrum, while "sample dimension" is the more general case of any measurement that appear in the cells of a coverage".
In fact these levels are not a real vertical CRS but a "kind of". Martin enhances that if we did an UML schema it should be drawned with a losange at its extremity.
They are levels of interests for different purposes :
- the PVU levels and MSL are used for forecasting
- tropopause, jet and ISO temperature levels are used for aeronautics, Even though temperature may appear here as a CRS it cannot be as it is not a monotonic function on the vertical.
- COTRA levels are used for militars needs.
In a way they could be seen as postprocessing made on the raw numerical model output for decision support in applied domains. Which in a way means they are really important for products that could be provided by WMS servers.
One proposal could be to define specific pre-defined names (analogous to the "current" for TIME) with no vertical datum attached to it. It might also be too restrictive to the words pre defined.
Jeff suggested a more flexible way : to provide In WMS Capabilities XML:
<Dimension name="computed_surface">0.7PVU, 1.5PVU, 2.0PVU, Tropopause, MSL, Jet_level, ISO_T0, 2nd_Iso_T0, etc</Dimension>
We rejected the proposal of putting the level into the name ( wind_speed_at_tropopause
Marie-Francoise will provide example of products for such specific levels.
There is still an issue on requesting at the same time products with an ELEVATION and products with a DIM_computed_surface.
This will be discussed at the next teleconf.
Could Oceanographers confirm if we should add a "density CRSs" analoguous to pressure levels ?
Next teleconf :
6 February 2012 : 16 UTC Telecon 1 24x7 EST
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- 02 Feb 2012