[CF-metadata] Grid mapping information

From: John Caron <caron>
Date: Mon, 19 Jul 2010 10:48:16 -0600

On 7/16/2010 2:12 AM, cristina.tronconi at artov.isac.cnr.it wrote:
> Helloevertybody,
> I have a netcdf file (chlorophyll gridded satellite daily map) in
> which I have my variable chl(tim,lat,lon), then the vector of regular
> lat and a vector for
> regular lon.
>
> My grid mapping is Equidistant Cylindrical. SO in the nc I set as
> GLOBAL ATTRIBUTE
> ----------------------------------
> attname=Conventions
> value=CF-1.4
>
> attname=grid_mapping
> value=Cylindrical
> ------------------------------------
> Some question:
> 1) A collegue of mine told me that for CF 1.4 the grid_mapping is no more
> a global attribute but it is a variable attribute named as
> "grid_mapping_name".
>
> BUT I run the CF checker for 1.4 on my file and everything is ok!!!!

The CF checker is limited in understanding the semantics, it often only
checks syntax.

>
> SO: Is it still correct /with cf 1.4) to set a global attribute as
> "grid_mapping" in the case (obviuosly) all the variables use the same
> grid_mapping? or must I put the same information as variable
> attribute? in this case, how?

I dont think a global attribute was ever CF compliant. Why do you think
it was?

In any case, you need to add an attribute to each data variable. see
examples in section 5.6

> 2) are "Equidistant Cylindrical" and "Cylindrical" still CF valid
> values for
> grid_mapping (or grid_mapping name)? I found only "Equirectangular" In
> the "Content Standard for Digital Geospatial Metadata. Federal
> Geographic Data Committee, FGDC-STD-001-1998" document mentioned in
> the Appendix F. Grid Mappings of CF 1.4.

We dont seem to have this projection in our list. Does anyone have
experience with it?
Received on Mon Jul 19 2010 - 10:48:16 BST