[CF-metadata] can a cell method be an attribute of an auxiliary coordinate variable ?

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 28 Feb 2014 18:34:39 +0000

Dear Randy

I think the answer is Yes and No! Only a data variable can have cell_methods,
but there is no prohibition on referring to a data variable as an aux coord var
by pointing to it from the coordinates attribute of another data variable.
So the air_pressure variable could be a data variable with an appropriate
cell_methods attribute, which would take the form "PIXEL: median" where PIXEL
is the name of some dimension which was collapsed to calculate the median.
Maybe this dimension does not exist, though? In that case I think it might
make sense to put "area: median". This would mean the median of all the values
within the area of that cell.

Cheers

Jonathan

----- Forwarded message from "rhorne at excaliburlabs.com" <rhorne at excaliburlabs.com> -----

> From: "rhorne at excaliburlabs.com" <rhorne at excaliburlabs.com>
> To: cf-metadata at cgd.ucar.edu
> Date: Thu, 27 Feb 2014 11:30:02 -0500
> Subject: [CF-metadata] can a cell method be an attribute of an auxiliary
> coordinate variable ?
>
>
> Dear All:
>
> i have a question ....
>
> We have a product containing an array of wind vectors (discrete sampling
> geometry of type point) all derived from consecutive scenes of hyper
> spectral imagery.
>
> One of the auxiliary coordinate variables is the air pressure. This air
> pressure is the median value of the imagery pixels used to derive the wind
> vector using a pattern recognition algorithm.
>
> There are no specific coordinates for the pixels that were used to derive
> the wind vector, but it would be useful to identify that the air pressure
> associated with the wind vector is a median value.
>
> Does it make sense to do the following in the specification of the air
> pressure auxiliary coordinate variable ?
>
> float pressure (number_of_wind_vectors);
>
> standard_name = "air_pressure"
>
> cell_methods = "air_pressure: median"
Received on Fri Feb 28 2014 - 11:34:39 GMT