Re: [netcdf-java] CDM Feature Types

• To: ngalbraith@xxxxxxxx
• Subject: Re: [netcdf-java] CDM Feature Types
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Wed, 07 Jul 2010 10:38:33 -0600

Hi Nan:

The working definitions are at

http://cf-pcmdi.llnl.gov/trac/wiki/PointObservationConventions.

but that site (or my home ISP) is down at the moment, so i cant give you a more 
specific URL.

In terms of your problem, station data has a fixed lat, lon, altitude. The data 
belonging to the station may have an additional z coordinate that is typically 
interpreted relative to the station altitude.

For more complicated topology, you might also consider the profile data type, 
which expects an array of data with varying z coordinates.

John


Nan Galbraith wrote:

Hi John -

The document at unidata.ucar.edu/software/netcdf-java/CDM/
does not include definitions for the feature types, and it points
to a word doc, CDM Feature Types which is labeled as a draft.
The definition of 'station' in that draft document has me a little
confused.

 > Station feature: a time-series of data points all at the same
 > location, with varying time (fixed x,y,z; ordered t).

Does this imply only that Z is fixed, or that it also must be a
single point?

In the OceanSITES project, our data is mainly 2-d time series,
with fixed X,Y, and fixed - but multiple - Z. We've added a
global attribute to our NetCDF files, 'cdm_data_type' which
we define as giving 'the Unidata CDM (common data model)
data type used by THREDDS. E.g. ...“Station”...' and advise
users to 'Use “Station” for OceanSITES mooring data.'

Can you please tell me if we're using the correct feature type?
I have a sinking feeling that Unidata has defined 'station' in
a very narrow way, which would make it inappropriate for
mooring data.

If these definitions are on line in a non-draft form, we'd like to
include a link to them in our Users Manual - but I've searched
the Unidata site and not found anything.

Thanks -
Nan Galbraith

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