All,
I'm trying to determine the right way to encode tide gauge data in CF.
I believe that the three applicable standard names are
sea_surface_height_above_geoid
sea_surface_height_above_sea_level
sea_surface_height_above_reference_ellipsoid
I don't think that we want to commit to any one of them, because the
data delivery service will be flexible enough to provide the data
referenced to various vertical datum so that the standard name in the
file might change based on a user request. I'm wondering how the
vertical datum is associated with the measurement indicated by the
standard name. For example, sea_surface_height_above_sea_level, implies
a datum of mean sea level. However, what if the user chooses another
reference sea level average such as MLLW, mean lower low water? Can
this be specified as an ancillary measurement or is it a coordinate
measurement? Similarly, how should the ellipsoid be specified in
sea_surface_height_above_reference_ellipsoid? Although this question is
probably more relevant to satellite data than tide gauges.
As an example you can see the NOAA National Water Level Observing
Network maintained by the NOAA National Ocean Service below. They are
creating a Sensor Observation Service that serves both observed and
predicted sea level data from tide gauge stations. The resulting data
is served using a GML dialect which allows for references to external
dictionaries specifying the vertical datum. Can something similar be
done in CF?
http://opendap.co-ops.nos.noaa.gov/ioos-dif-sos/
click Try Me (GET/POST) next to Preliminary Water Level Data (Latest)
for an example interface that provides the data in gml/xml. Inside the
file you'll see the reference to VerticalDatum.
Thanks for your time.
Derrick
--
Derrick Snowden
NOAA Climate Program Office, Climate Observation Division
1100 Wayne Avenue, Suite 1202
Silver Spring, MD 20910 USA
Tel 1-301-427-2464
Fax 1-301-427-0033
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Received on Fri Feb 27 2009 - 10:07:14 GMT
