Dear Mike
In a collection of trajectories comprising a feature of trajectory type, the
time coordinate does not have to be the same for each trajectory. This is
required only in the orthogonal representation (sect 9.3.1), not the
incomplete or the two ragged representations (9.3.2-4).
Best wishes
Jonathan
----- Forwarded message from Mike Godin <mikegodin at yahoo.com> -----
> Date: Tue, 18 Mar 2014 13:50:19 -0700
> From: Mike Godin <mikegodin at yahoo.com>
> To: Jim Biard <jbiard at cicsnc.org>, "CF-metadata at cgd.ucar.edu"
> <CF-metadata at cgd.ucar.edu>
> Subject: Re: [CF-metadata] Classification of a "trajectory" with asynchronous
> time coordinates
> X-Mailer: YahooMailWebService/0.8.178.641
>
> Hi Jim,
>
> Actually, the latitude, longitude, and z values are not sampled at different rates (I showed them as such for an extreme example, and in some decimation schemes they end up being asynchronous), but in reality the science data are collected asynchronously from each other and the coordinate data.??
>
> I can't find where the CF standard specifies that a trajectory must have a single time dimension (perhaps I've missed it). ??If it does, and this is a collection of time series, can a collection of time series be represented in a CF-compliant file? ??If so how would one indicate that lat, lon, and z are the coordinates through which O3 and NO3 vary? ??
>
> If it helps, one??could imagine the following somewhat simpler CDL, in which coordinates are time-synchronized but scientific measurements are not:
>
> ?? dimensions:
> ?? ?? ?? time_coords = 435;
> ?? ?? ?? time_O3 = 335;
> ?? ?? ?? time_NO3 = 5357;
>
> ?? ??variables:
> ?? ?? ?? double time_coords(time_coords) ;??
> ?? ?? ?? ?? ?? time_coords:standard_name = "time";
> ?? ?? ?? ?? ?? time_coords:long_name = "time_coords" ;
> ?? ?? ?? ?? ?? time_coords:units = "days since 1970-01-01 00:00:00" ;
> ?? ?? ?? float lon(time_coords) ;??
> ?? ?? ?? ?? ?? lon:standard_name = "longitude";
> ?? ?? ?? ?? ?? lon:long_name = "longitude" ;
> ?? ?? ?? ?? ?? lon:units = "degrees_east" ;
> ?? ?? ?? float lat(time_coords) ;??
> ?? ?? ?? ?? ?? lat:standard_name = "latitude";
> ?? ?? ?? ?? ?? lat:long_name = "latitude" ;
> ?? ?? ?? ?? ?? lat:units = "degrees_north" ;
> ?? ?? ?? float z(time_coords) ;??
> ?? ?? ?? ?? ?? z:standard_name = ???altitude???;
> ?? ?? ?? ?? ?? z:long_name = "height above mean sea level" ;
> ?? ?? ?? ?? ?? z:units = "km" ;
> ?? ?? ?? ?? ?? z:positive = "up" ;??
> ?? ?? ?? ?? ?? ??z:axis = "Z" ;??
> ?? ?? ?? ?? ?? ??
> ?? ?? ??double time_O3(time_O3) ;??
> ?? ?? ?? ?? ?? time_O3:standard_name = "time";
> ?? ?? ?? ?? ?? time_O3:long_name = "time_O3" ;
> ?? ?? ?? ?? ?? time_O3:units = "days since 1970-01-01 00:00:00" ;
> ?? ?? ?? float O3(time_O3) ;??
> ?? ?? ?? ?? ?? O3:standard_name = ???mass_fraction_of_ozone_in_air???;
> ?? ?? ?? ?? ?? O3:long_name = "ozone concentration" ;
> ?? ?? ?? ?? ?? O3:units = "1e-9" ;
> ?? ?? ?? ?? ?? O3:coordinates = "time_O3 lon lat z" ;
>
> ?? ?? ??double time_NO3(time_NO3) ;??
> ?? ?? ?? ?? ?? time_NO3:standard_name = "time";
> ?? ?? ?? ?? ?? time_NO3:long_name = "time_NO3" ;
> ?? ?? ?? ?? ?? time_NO3:units = "days since 1970-01-01 00:00:00" ;
> ?? ?? ?? float O3(time_NO3) ;??
> ?? ?? ?? ?? ?? NO3:standard_name = ???mass_fraction_of_nitrate_radical_in_air???;
> ?? ?? ?? ?? ?? NO3:long_name = "NO3 concentration" ;
> ?? ?? ?? ?? ?? NO3:units = "1e-9" ;
> ?? ?? ?? ?? ?? NO3:coordinates = "time_NO3 lon lat z" ;
>
> ?? ??attributes:
> ?? ?? ?? :featureType = "????";
>
> Thanks,??
> Mike Godin
>
> Lead Engineer,??
> IntuAware
> http://intuaware.com
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
----- End forwarded message -----
Received on Sat Nov 08 2014 - 15:12:56 GMT
