[CF-metadata] CF Section 5.3 "Reduced Horizontal Grid" and Section 8.2 "compression by gathering" somewhat inconsistent

[John Caron]

One thing i forgot to mention, in the 5.3 example:

> 
> Example 5.3. Reduced horizontal grid
> 
> dimensions:
>   londim = 128 ;
>   latdim = 64 ;
>   rgrid = 6144 ;
> variables:
>   float PS(rgrid) ;
>     PS:long_name = "surface pressure" ;
>     PS:units = "Pa" ;
>     PS:coordinates = "lon lat" ;
>   float lon(rgrid) ;
>     lon:long_name = "longitude" ;
>     lon:units = "degrees_east" ;
>   float lat(rgrid) ;
>     lat:long_name = "latitude" ;
>     lat:units = "degrees_north" ;
>   int rgrid(rgrid);
>     rgrid:compress = "latdim londim";

there seems to be actually no use, or need for, the latdim and londim dimensions or the rgrid variable. what it looks like from the outside is a set of random points, each point has an explicit lat,lon coordinate. Presumably the rgrid "compression index" tells you something about it really being a 2D grid. Exactly what it says about grid connectivity is not immediately obvious.