[CF-metadata] curvilinear cartesian coordinates case

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 1 Dec 2006 21:46:47 +0000

Dear Brian and John

> John proposed a new object ...
>
> That's not using the grid_mapping variable to point to the projection
> coordinates. It's defining a new object that contains both the projection
> coordinates and the grid mapping.

Oh, I see. Sorry, I jumped to a conclusion, but now I have reread what John
said I get the point. We have three options:

John's

  int Dutch_CoordSystem;
    Dutch_CoordSystem:coordinates = "dutch_x dutch_y";
    Dutch_CoordSystem:grid_mapping = "EPSG19914";
  int German_CoordSystem;
    German_CoordSystem:coordinates = "german_x german_y";
    Dutch_CoordSystem:grid_mapping = "EPSG16362";
  float velocity(time,layer,m,n);
    velocity:coordinateSystems = "Dutch_CoordSystem Belgian_CoordSystem" ;
    velocity:coordinates="lat lon";
  float dutch_x(m,n);
  float dutch_y(m,n);
  float german_x(m,n);
  float german_y(m,n);

mine

  float velocity(time,layer,m,n);
    velocity:grid_mapping="dutch_x: dutch_y: EPSG19914 german_x: german_y: EPSG16362";
    velocity:coordinates="lat lon";
  float dutch_x(m,n);
  float dutch_y(m,n);
  float german_x(m,n);
  float german_y(m,n);

Bert's

  float velocity(time,layer,m,n);
    velocity:coordinates="lat lon dutch_x dutch_y german_x german_y";
  float dutch_x(m,n);
    dutch_x:grid_mapping="EPSG19914";
  float dutch_y(m,n);
    dutch_y:grid_mapping="EPSG19914";
  float german_x(m,n);
    german_x:grid_mapping="EPSG16362";
  float german_y(m,n);
    german_y:grid_mapping="EPSG16362";

I appreciate that John's scheme, by introducing an extra indirection, saves
repeating the association of the grid_mapping and the projection variables,
which must be done on every data variable in my scheme, and on every
projection variable in Bert's. I'm not convinced that the extra complexity is
really needed to solve this problem, though.

Cheers

Jonathan
Received on Fri Dec 01 2006 - 14:46:47 GMT