[CF-metadata] Encoding Errors on variables in CF

[John Evans]

Hi folks,

I'm starting to get a little lost here, so I'm going to drum up another
example.  Just a little background, our met sensors produce two different
estimates for wind direction, on being a unit vector average, and the other
not being unit vector.  They also return standard deviations for each, and
then the on-shore processing computes data quality.  Some attributes not
pertinent to this particular discussion are removed.

       double wind_depth(wind_depth) ;
                wind_depth:positive = "down" ;
.
.
.
       float wind_direction_uv(time, wind_depth, lat, lon) ;
                wind_direction_uv:long_name = "Unit Vector Wind Direction" ;
		wind_direction_uv:standard_name = "wind_from_direction" ;

   	float wind_direction_uv_stddev(time, wind_depth, lat, lon) ;
                wind_direction_uv_stddev:long_name = "Wind Direction Standard
Deviation" ;
		wind_direction_uv_stddev:intent = "standard_error" ;
		wind_direction_uv_stddev:ancillary_variable_for = "wind_direction_uv" ;

        byte wdir_uv_qc(time, wind_depth, lat, lon) ;
                wdir_uv_qc:long_name = "Wind Direction Quality" ;
		wdir_uv_qc:intent = "data_quality" ;
		wdir_uv_qc:ancillary_variable_for = "wind_direction_uv" ;
		wdir_uv_qc:flag_values = 0b, 1b; 2b ;
		wdir_uv_qc:flag_values = "quality_good out_of_range sensor_nonfunctional" ;
.
.
.
       float wind_direction_ve(time, wind_depth, lat, lon) ;
                wind_direction_ve:long_name = "Vector Mean Wind Direction" ;
		wind_direction_ve:standard_name = "wind_from_direction" ;

   	float wind_direction_ve_std(time, wind_depth, lat, lon) ;
                wind_direction_ve_std:long_name = "Wind Direction Standard
Deviation" ;
		wind_direction_ve_std:intent = "standard_error" ;
		wind_direction_ve_std:ancillary_variable_for = "wind_direction_ve" ;

        byte wdir_ve_qc(time, wind_depth, lat, lon) ;
                wdir_ve_qc:long_name = "Wind Direction Quality" ;
		wdir_ve_qc:intent = "data_quality" ;
		wdir_ve_qc:ancillary_variable_for = "wind_direction_ve" ;
		wdir_ve_qc:flag_values = 0b, 1b; 2b ;
		wdir_ve_qc:flag_values = "quality_good out_of_range sensor_nonfunctional" ;

On Friday 11 April 2003 14:50, Russ Rew wrote:
> Ag,
>
> > I think that Russ's suggestion about prefixing "for_variable_" or
> > "for_variables_" is fine. As long as this becomes a standard it probably
> > doesn't matter too much what is decided on as long as the link is clear.
> > The one-to-one and one-to-many mappings will also be potentially useful
> > in making it clear to the user what variables are related in a file(s?).
>
> Just to be clear, I didn't actually propose (or intend to propose) any
> prefixes such as "for_variable_" or "for_variables_".  Instead I
> proposed just using a variable attribute named "for_variable" or
> "for_variables" to capture the intent that a variable provides
> ancillary information for another variable.
>
> Typically, attributes are used for ancillary information about a
> variable.  However, in the netCDF data model, attributes can't have
> attributes (such as units) and can't be multidimensional.  So when the
> ancillary information is sufficiently complex, you need to store it in
> another variable instead of in an attribute.  In such cases, I'm
> recommending identifying the variable or variables to which the
> ancillary information applies with an attribute named "for_variable"
> or "for_variables" which has as its value a string that names the
> variable(s) to which the ancillary information applies.
>
> --Russ
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://www.cgd.ucar.edu/mailman/listinfo/cf-metadata



-- 
John Evans           
johnevans at acm.org