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[CF-metadata] metadata for regularly spaced data and averages

From: Jim Biard <jbiard>
Date: Mon, 23 Jul 2018 16:56:16 -0400

Eli,

I'm not quite sure what you are looking for here. There are no other
mechanisms in CF right now for describing sampling interval. Perhaps it
would help if you described in greater detail the inputs to your process
and the outputs from your process that you wish to store in a netCDF
file. Here's what I am getting from what you wrote in your first
message, with arbitrary numbers selected to make it concrete.

Inputs:

    Each hour:

      * Instrument takes 100 samples
      * Instrument reports the time and the average of the 100 samples

Outputs for a netCDF file:

  * One month of hourly average values
  * The time each hourly average was reported
  * The length of the acquisition interval

If this is what you have it is straightforward to store in netCDF using
CF. Using CDL, the file structure would be:

    netcdf file: sample.nc {
     ??? dimensions:
     ??????? time = 100;
     ??????? bnds = 2;
     ??? variables:
     ??????? float time(time);
     ??????????? time:long_name = "reporting time";
     ??????????? time:units = "seconds since 1970-01-01 00:00:00";
     ??????????? time:standard_name = "time";
     ??????????? time:axis = "T";
     ??????????? time:calendar = "gregorian";
     ??????????? time:bounds = "time_bounds";
     ??????? float time_bounds(time, bnds);
     ??????? float data(time);
     ??????????? data:long_name = "The data";
     ??????????? data:cell_methods = "time: mean (any comment that you
    find helpful)";
     ??????????? data:standard_name = "?????";
     ??????????? data:units = "????";
     ??? data:
     ??????? time = 3600.0, 7200.0, ... ;
     ??????? time_bounds = 0.0, 3600.0,?? 3600.0, 7200.0,? 7200.0,
    10800.0,?? ... ;
    }

I hope this helps frame the question and/or provides a bit of the answer.

Grace and peace,

Jim

On 7/20/18 5:42 PM, Ateljevich, Eli at DWR wrote:
>
> I have data that are recorded hourly after sampling the previous hour.
> The original sampling rate is high, but in some cases not provided so
> it doesn?t tend to make it into the metadata.
>
> I can represent the hourly average with cell_methods and time_bnds,
> but it is painful for two reasons:
>
> 1. It costs some storage overhead in simple cases because the bounds
> are obvious.
>
> 2. The fact that it is regularly sampled is part of the station
> design. Here, I have to infer two things: (regular reporting interval
> and relative position of timestamp from time_bnds). The first one in
> particular is not a comment to me.
>
> I can certainly see the lack of generality creeping looming, but this
> is such an important special case. Is there no common shorthand or
> possibly something I could at least do in **addition** to the
> cell_bounds. ?Am I missing a long conversation on this?
>
> Obviously my question extends to any regular sampling geometries, I
> just picked a simple one in 1D.
>
> Thanks,
>
> Eli
>
>
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata

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