[CF-metadata] CF point observation Conventions

Nan Galbraith ngalbraith at whoi.edu
Tue Feb 28 13:33:53 MST 2012


Hello all -

I'd been hoping that I would not outlive my ability to ignore the CF 
FeatureTypes,
but apparently it's not to be. As a fallback position, now I'm hoping 
that we can
add a type, to accommodate data collected on stationary moorings, where 
there
are time series of variables at a single x,y location, at multiple 
depths, on a single
time base. The majority of the data in the OceanSITES project fits into 
this category,
and there is no existing feature type to describe it, as far as I 
understand.

Presently, to use any of the feature types, we would need to store data 
from each
depth in an individual file. This is a serious problem, in part because 
we have
dozens of instruments - 30 or 40 in some cases - on each mooring, but also
because, for most of our data users, the most convenient files contain 
z-merged
data; for example, a single time series containing all the temperatures 
and salinities.

Back in 2009, I made the suggestion to change the list of types that 
cover time series,
from the single:
   * stationTimeSeries: a time-series of data points at the same 
location, with varying time
to the pair:
   * TimeSeries: a time-series of data points at one X,Y,Z with varying T
   * stationTimeSeries: a time-series of data points at one X,Y, with 
multiple Z and T

or, alternatively,to change the definition of stationTimeSeries to 
something like 'a
time-series of data points at one geographical location and one or more 
depths'.

The exact terms don't matter much to me (although there's a cultural problem
with including the word 'profile' in the name of a 2D timeseries) but we 
still DO
need a way to describe these stations.

Here's an excerpt from a CDL for a typical moored station's data.
dimensions:
         TIME = 129139 ;
         DEPTH = 16 ;
         LATITUDE = 1 ;
         LONGITUDE = 1 ;
variables:
         double TIME(TIME) ;
                 TIME:standard_name = "time" ;
         double DEPTH(DEPTH) ;;
                 DEPTH:standard_name = "depth" ;
         double LATITUDE(LATITUDE) ;
                 LATITUDE:standard_name = "latitude" ;
         double LONGITUDE(LONGITUDE) ;
                 LONGITUDE:standard_name = "longitude" ;
         double TEMP(TIME, DEPTH) ;
                 TEMP:standard_name = "sea_water_temperature" ;
                 TEMP:coordinates = "TIME, DEPTH, LATITUDE, LONGITUDE" ;

There are several threads in the CF mail archive about this, mostly
under subject lines containing the phrase 'point obs' - but as far
as I know, it was never resolved, at least not to the satisfaction of
those who work with mooring data.

Regards -
Nan

-- 
*******************************************************
* Nan Galbraith        Information Systems Specailist *
* Upper Ocean Processes Group            Mail Stop 29 *
* Woods Hole Oceanographic Institution                *
* Woods Hole, MA 02543                 (508) 289-2444 *
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