[CF-metadata] CF point observation Conventions ready for review

From: John Caron <caron>
Date: Mon, 16 Nov 2009 19:12:17 -0700

Hi Roy, Nan:

Let me try to see where the mapping between the two classifications is
currently at:

Lowry, Roy K wrote:
> Dear All,
>
> I come from Nan's community with the added complication of exposure to CSML through working with NDG. From this position in BODC we have developed a collection of feature type names that my intention is to map to the CF feature type names once John's work is complete. As I watch the development of the proposal I'm starting to get uneasy feelings that this mapping is getting harder as the feature type definitions become more fluid, which echoes Nan's feelings that the proposal is drifting away from her domain.
>
> The feature terms we use for observational data in BODC are:
>
> Profile - single set of measurements with single (by assumption) x, y, t values but varying spatial z. An example is a single, fully processed (i.e. binned) CTD cast.
>
this is a single profile; a single feature in a file is considered a
special case of multiple features in a file, with some special handling
to allow scalar coordinate variables.
> Profile collection - an aggregation of profiles into a single data object. An example is all the CTDs from a section or a cruise.
>
sounds like a "section", a connected set of profiles along a trajectory.
If you dont care about the "along a trajectory" then its just a
collection of profiles.
> Profile series - a set of measurements with single x,y a fixed set of spatial z values and progessing t. An example is a single moored ADCP deployment record.
>
a single "stationProfile". station is synonomous with timeSeries, so we
could just as well call it timeSeriesProfiles. A special case of a
collection of stationProfile.
> Point - a set of measurements with single x, y, and z and progressing t. Example is a single moored recording current meter record.
>
a special case of a stationTimeSeries collection, with only one station
in the file. A station is a named x,y (optional z) location.
> Point collection - an aggregation of point features in a single container. Example is all the records from all the current meters on a mooring or deployed on a cruise.
>
possibly a point collection, if you think of these as unconnected.
> Spectrum series - a set of measurements with single x,y a fixed set of non-spatial z values and progessing t. An example is a power spectrum time series from a wave recorder.
>
a special case of a stationTimeSeries collection, with a
non-georeferencing dimension. we would not refer to the wavelength
dimension as z just to keep things clear.
> 2D-trajectory - a set of measurements with variable x, y, t and a single spatial z. Example is the thermosalinograph record from a cruise.
>
A trajectory with a scalar z coordinate.
> 3D-trajectory - set of measurements with variable x, y, t and a variable spatial z. Example is the thermosalinograph record from an AUV mission. It is also applicable to a yo-yo CTD station, mirroring Chris's comments on atmospheric "profiles" with variant x,y.
>
A trajectory with a z coordinate.
> I think that Nan and most of the observational oceanographic community recognise these concepts and consequently, if a mapping to them to your feature definitions is maintained then it will help keep us on board.
>
> Note that the difference between 'point' and 'point collection' is important to me as on observational data manager, which is a different perspective to an observational data ingestor.
>
Im not sure if I have captured the difference correctly. What do you think?
> Cheers, Roy.
Im not particularly attached to the names, as long as they are clear and
can be explained easily. Nan suggested:

You could change the list of types that cover profiles and time series
from:
   * stationTimeSeries: a time-series of data points at the same
location, with varying time
   * profile: a set of data points along a vertical line
   * stationProfile: a time-series of profiles at a named location

to something like:
   * 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
   * profile: a set of data points along a vertical line
   * stationProfile: a time-series of profiles at a named location

which i think amounts to renaming "stationTimeSeries" to "timeseries"
(ok with me, anyone else care?). however "stationTimeseries: a
time-series of data points at one X,Y, with multiple Z and T" probably
needs a bit more thinking. Im not all that clear how the two differ. Is
"timeseries" intended to be only for surface data?

I think the main case thats not clear is station data with different z
coordinates for different measurements. I still have to generate an
example of that and see if we need to add something to the proposal.
Received on Mon Nov 16 2009 - 19:12:17 GMT