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Re: [ferret_users] sample_dimension in ferret

Hi Hella,

The other attribute that's needed is "cf_role", as an attribute on a variable which will identify the station (or trajectory, or whatever the feature type is, in general). Your file doesn't seem to have a variable that is a station id. This is described in the CF conventions but it looks like we need to add this information to the Ferret documentation about Discrete Sampling Geometries files.


On 3/8/2017 8:07 AM, Hella Riede wrote:
Hello ferreters,

I checked out the ferret documentation website about discrete geometries http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/data-set-basics/2-8-discrete-geometries-datasets-1, especially about the attribute 'sample_dimension'.

Based on http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html#_contiguous_ragged_array_representation_of_time_series, I made a simple dataset, see attachments, containing the 'sample_dimension' attribute.

When I load this simple example into ferret, I don't get the observations on the X axis and the instance axis ('station') in E direction as described on the ferret website above, but rather two X grids instead, see output below.

Any idea why? Is the 'dsg_file.nc' dataset used in the ferret example available somewhere to better understand the structure?

I am not sure if 'obs' should be the sum of all observations of all stations which 'rowsize' will then divide up per station, or if 'obs' should be the maximum length per 'station'.

Thanks in advance!

Best wishes,
on FERRET v7.022 (beta/debug)

yes? use ragged.nc
yes? sh da
      currently SET data sets:
     1> ./ragged.nc  (default)
  name     title                             I         J K         L
  LON      station longitude                1:3       ... ...       ...
  LAT      station latitude                 1:3       ... ...       ...
  ROWSIZE  number of observations for this  1:3       ... ...       ...
  TEMP     temperature                      1:11      ... ...       ...
  yes? sh grid temp
     GRID GNN2
  name       axis              # pts   start end                 subset
  OBS       X                   11 r   1 11                  full
  normal    Y
  normal    Z
  normal    T
yes? sh grid rowsize
     GRID GNN1
  name       axis              # pts   start end                 subset
  STATION   X                    3 r   1 3                   full
  normal    Y
  normal    Z
  normal    T

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