Peter and Kerian,
I think that it's a good idea to start collecting requirements and to investigate what WCS can and can't do. I believe that until this point, WCS deals with "grid coverage" only but not more general coverage types including feature coverage (vector data types). Thus, WCS essentially is for N-dimensional data arrays, especially those having two of the N dimensions associated to two near horizontal geographic/projected coordinate reference system.
A 1-D time series data array, e.g., Data(time) at a fixed location can be considered as a special case of 3-D, with the two horizontal Ds fixed at one point, e.g., Data(time,lat,lon) where the dimension sizes of lat and lon are one.
A 2-D time series vertical profile data array, e.g., Data(time,pressure) at a fixed location can be considered as a special case of 4-D, with the two horizontal Ds fixed at one point, e.g., Data(time,pressure, lat,lon) where the dimension sizes of lat and lon are one.
Similarly, a data array of any n-D fixed at one location can be considered as
(n+2)-D by adding two spatial Ds having dimension sizes being one.
Multiple n-D data arrays at multiple locations or one (n+1)-D data array, where none of
the "n-D" is horizontal spatial dimension, can be considered a (n+1)-D coverage
with one of the dimension indicating a spatial location. This dimension that indicates
spatial location may be an location ID, lookup table, etc which can be associated with a
2-D near horizontal position. This dimension can be indicated using an Engineering
coordinate axis such a locationID, profilePosition, etc. How can such n-D or (n+1)-D
data array, or coverage, be handled in WCS? How about more complicated data structures
such as meshes described in Kerian's email? I guess that the best way is to list use
cases/requirements as Peter suggested.
Wenli
BTW, it will be very helpful if someone can provide this (GALEON or metaocean community) a clear definition/explanation of feature (feature is an abstraction of a real world phenomenon and thus it is everything), coverage, coverage feature (coverage is a subtype of feature), feature coverage, etc.
Keiran-
it is exciting for us WCSers to get a clearer pic on what is actually
wanted when talking about irregular meshes. Can we somehow start
collecting requirements in an ordered manner, say a Wiki page?
What I am most interested in:
- data structures: all information about what you expect (eg: general
TINs vs warped grids)
- operations: you mention subsetting, what about others? reprojection I
guess?
Note that WCPS (Web Coverage Processing Service), a WCS extension,
allows processing of coverages, and extending this in parallel makes me
ask deeper here.
- formats: NetCDF, of course ;-) ...any other formats wanted by the
communities?
- "anything else" that contributes to the scenario - in the end, some
use case scenarios IMHO serve best.
We might start with a matrix for the communities (is metocean one or
several in this respect?) and gradually massage it into one requirements
list for presentation to the WCS group.
@Ben: as the WCS Twiki is not open to all on this list, could we have
some place with r/w access for all GALEON people on the GALEON Wiki?
-Peter
