[CF-metadata] vector quantities (e.g. velocities) in CF-NetCDF

From: Bryan Lawrence <b.n.lawrence>
Date: Fri, 27 Apr 2007 18:11:13 +0100

> For particular purposes, programs need to know "scientific" relations of this
> kind, but we can't possibly encode all such relationships in the netCDF file.
> That is not metadata, but instructions on what you can do with the data.

define metadata for me! If that's not metadata, I don't know what is!
It's a separate point as to whether it belongs in CF and if so,
where ... Surely knowing about vectors
is something we care about?

> My proposal therefore would be that we maintain another table in a machineable
> form listing the components of vectors (for your case). We can compile this
> table now from the standard name table, and add to it as we add to the standard
> name table. Possibly some ingenious system of flags in the standard name table
> itself might avoid the need for a separate table.
>
> Some relationships can be deduced, given the systematic construction
> of standard names. If you open your file, read in a list of all the standard
> names which occur in it, and do something like this to the list:
> s/northward/NE/
> s/eastward/NE/
> then identical results will occur in pairs for vectors expressed as northward
> and eastward components. But other cases can't be dealt with like this, so
> a table is needed in general.

I think that would a far more cumbersome solution, than say, defining a
variable attribute which took a value which could be used as a vector
basket, e.g.

var u:
 attribute:vector_parent=wind
var v:
 attribute:vector_parent=wind

with apologies for not using the right notation, I'm kind of frantic
right now, and don't even know why I'm doing this instead of what I
should be ...

where the "wind" thing can be any string the user wants to use as a
label ...

Cheers
Bryan
Received on Fri Apr 27 2007 - 11:11:13 BST