[CF-metadata] Conventions for Unstructured Grid Data

From: Brian Eaton <eaton>
Date: Thu, 18 Nov 2004 09:16:32 -0700

All,

I agree with Steve's general comments on the current proposal. And I agree
with adding new attributes to point to the variables that will describe
properties of the mesh. The only thing I'd like to modify about Steve's
proposal is that rather than attaching those attributes directly to the
dependent variables, I'd prefer an analogous approach to the one we chose
(after a lengthy discussion) for describing grid mappings. In this case
we're trying to describe the grid, so I propose a "grid" attribute to
attach to the dependent variable, and that attribute points to a variable
which just acts as a container for all the specific attributes needed to
describe connections and boundary nodes for a particular type of mesh.
I've modified the original proposal to illustrate the idea, without having
given much thought to whether or not the specific attribute names are the
best ones.

netcdf umesh_cf {
dimensions:
  node = 9700 ;
  nele = 17925 ;
  nbnd = 1476 ;
  nface = 3 ;
  nbi = 4 ;
  sigma = 1 ;
  time = UNLIMITED ; // (0 currently)
variables:
  float time(time) ;
    time:long_name = "Time" ;
    time:units = "days since 2003-01-01 0:00:00 00:00" ;
    time:base_date = 2003, 1, 1, 0 ;
    time:standard_name = "time" ;
  float lon(node) ;
    lon:long_name = "Longitude" ;
    lon:units = "degrees_east" ;
    lon:standard_name = "longitude" ;
  float lat(node) ;
    lat:long_name = "Latitude" ;
    lat:units = "degrees_north" ;
    lat:standard_name = "latitude" ;
  float depth(node) ;
    depth:long_name = "Bathymetry" ;
    depth:units = "meters" ;
    depth:positive = "down" ;
    depth:standard_name = "depth" ;
    depth:grid = "grid_description";
  char grid_description
    mesh:grid_name = "triangular_mesh";
    mesh:Horizontal_Triangular_Element_Incidence_List = "ele";
    mesh:Boundary_Segment_Node_List = "bnd";
    mesh:index_start = 1;
  int ele(nele, nface) ;
  int bnd(nbnd, nbi) ;


Brian
Received on Thu Nov 18 2004 - 09:16:32 GMT