Hi John,
You are correct that the latitude and longitude auxillary coordinate
variables should be identified by using the coordinates attribute.
The warning that the CF checker should have given is that latitude and
longitude are multidimensional coordinate variables whose name matches the
name of one of their dimensions. We recommended against this in the CF doc
to avoid the potential confusion with coordinate variables as defined in
the netCDF User's Guide. That confusion is manifested in this file's
metadata as apparently the author expects the latitude and longitude
variables to be identified as coordinate data since the variable names
match dimension names.
I believe the checker is correct in saying there are no errors since it can
only check for syntax errors. There's no way for it to know that the
author intended certain variables to have latitude and longitude
coordinates. The checker could be improved, however, to give "expert
analysis" of the metadata. For example, in addition to reporting syntax
errors, it could give a summary of the coordinates associated with each
variable. A data writer could use this information to verify that his
intentions were being correctly expressed in the metadata.
Brian
On Thu, Jul 03, 2003 at 01:22:43PM -0600, John Caron wrote:
> below is the ncdump of a file. the CF convention checker passes it with
> "0 errors". my parser doesnt find the 2D latitude, longitude coordainte
> variables, because i assumed that they have to be named by a
> "coordinate" attribute (section 5.2). Opinions?
>
> netcdf C:\data\conventions\cf\signell_july2_03.nc {
> dimensions:
> s_rho = 20; // (has coord.var)
> latitude = 60;
> longitude = 160;
> time = UNLIMITED; // (2 currently) // (has coord.var)
>
> variables:
> double Cs_r(s_rho);
> :long_name = "S-coordinate stretching curves at RHO-points";
> :valid_min = -1.0; // double
> :valid_max = 0.0; // double
> double theta_s;
> :long_name = "S-coordinate surface control parameter";
> double theta_b;
> :long_name = "S-coordinate bottom control parameter";
> double h(latitude, longitude);
> :long_name = "bathymetry at RHO-points";
> :units = "meter";
> double hc;
> :long_name = "S-coordinate parameter, critical depth";
> :units = "meter";
> double latitude(latitude, longitude);
> :long_name = "latitude of RHO-points";
> :units = "degrees_north";
> double longitude(latitude, longitude);
> :long_name = "longitude of RHO-points";
> :units = "degrees_east";
> double s_rho(s_rho);
> :long_name = "S-coordinate at RHO-points";
> :valid_min = -1.0; // double
> :valid_max = 0.0; // double
> :standard_name = "ocean_s_coordinate";
> :positive = "up";
> :formula_terms = "s: s_rho eta: zeta depth: h a: theta_s b: theta_b
> depth_c: hc";
> float temp(time, s_rho, latitude, longitude);
> :long_name = "potential temperature";
> :units = "Celsius";
> double time(time);
> :long_name = "time since initialization";
> :units = "seconds since 1968-05-23 00:00:00 UTC";
> :calendar = "gregorian";
> float zeta(time, latitude, longitude);
> :long_name = "free-surface";
> :units = "meter";
>
> // Global Attributes:
> :Conventions = "CF-1.0";
> :type = "ROMS/TOMS output averages file";
>
> }
>
>
>
> File name: C:\data\conventions\cf\signell_july2_03.nc
>
>
> --------------------------------------------------------------------------------
> Output of CF-Checker follows...
>
> CHECKING NetCDF FILE
> =====================
>
> ------------------
> Checking variable: theta_b
> ------------------
>
> ------------------
> Checking variable: Cs_r
> ------------------
>
> ------------------
> Checking variable: temp
> ------------------
>
> ------------------
> Checking variable: h
> ------------------
>
> ------------------
> Checking variable: longitude
> ------------------
>
> ------------------
> Checking variable: s_rho
> ------------------
>
> ------------------
> Checking variable: theta_s
> ------------------
>
> ------------------
> Checking variable: time
> ------------------
>
> ------------------
> Checking variable: latitude
> ------------------
>
> ------------------
> Checking variable: hc
> ------------------
>
> ------------------
> Checking variable: zeta
> ------------------
>
> ERRORS detected: 0
> WARNINGS given: 0
>
>
>
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Received on Thu Jul 03 2003 - 16:25:36 BST
