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#113: Review of CF feature types
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Reporter: mgschultz | Owner: cf-conventions@…
Type: | Status: new
enhancement | Milestone:
Priority: medium | Version:
Component: cf- | Keywords: featureType, Grid, Point,
conventions | TimeSeries, Profile
Resolution: |
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Comment (by mgschultz):
Replying to [comment:14 jonathan]:
> Dear Martin
>
> Thanks for this list. I think I must be missing something basic, because
I don't understand the purpose of the rectified coverages. They look like
gridded 1D-, 2D- and 3D data variables. Chapter 9 of CF was introduced to
enable efficient and convenient storage of collections of 0D- and 1D data
variables which have a variety of dimensions and coordinates, because to
store each feature in its own data variable (which is logically
equivalent) would require a very large number of netCDF dimensions and
coordinate variables and would produce a rather cumbersome file. When you
say that you hope the rectified coverage types could be added to CF, do
you mean that this same storage problem arises with gridded fields as
well?
>
> Best wishes and thanks
>
> Jonathan
Hi Jonathan,
thanks for your comment. This distinction between "rectified" and
"non-rectified" grid coverages reflects the alignment of the gridded data
along the coordinate axes. A global model output will usually consist of a
(more or less) regular grid, so you will find, for example
temperature(time, lev, lat, lon). This is a rectified grid, because you
can describe the lon and lat values by 1d-coordinate variables lon(lon)
and lat(lat). If, on the other hand, you have a rotated grid, the variable
will be temperature(time, lev, y, x), and the coordinate variables will be
lon(y,x) and lat(y,x). This requires different processing when you want to
put the data onto a map or extract a subset, etc. This is why I
distinguish "nonrectified" from "rectified" (grid) coverages.
Cheers,
Martin
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Ticket URL: <http://cf-pcmdi.llnl.gov/trac/ticket/113#comment:16>
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