Hello again,
I'm forwarding the message below to the galeon email list; the
original message bounced because only members of the list can post to
the list.
It appears that discussions of topics related to the OGC GALEON
Interoperability Experiment have generated interest with several
individuals who are not on the galeon email list. My current approach
is to forward those messages to the list and subscribe the sender to
the list. Of course, I will remove anyone from the list who so
desires.
I've also created a set of web pages related to WCS GALEON (Web
Coverage Service Geo-interface to Atmosphere, Land, Earth, Ocean
NetCDF).
http://www.unidata.ucar.edu/projects/THREDDS/GALEON/Home.html
where we are posting background and status information about GALEON.
-- Ben Domenico
Unidata Deputy Director
GALEON Initiator
---------- Forwarded message ----------
From: Simon.Cox@xxxxxxxx
Yes.
Perhaps the most important differences between the GML/ISO concept of
"coverage" and netCDF and allies are:
1. netCDF etc support rather generalised mappings between arrays. Thus the
"domain" of the data (the independent variable, if you like) is not really
contrained.
In contrast, a geospatial coverage is a specialisation in which the domain must
be spatio-temporal, i.e. between 1 and 4 dimensions. As Ron points out, JP2K
is even more restricted in this sense - it only supports 2D domains.
2. There is explicit support for registering the domain of a geospatial
coverage to real-world locations - the most well-known is where the domain is a
rectified grid, but other geometries may be used which are tied to a spatial
reference system.
3. As Ron points out, an "Observation" is the act of collecting some values associated with a
target. The "result" of an observation is essentially parallel to the "range" in a
coverage.
The "target" of an observation is parallel to the "domain".
The Observation viewpoint focusses on the observation event, and is primarily a
means to access metadata associated with property values - how they were
obtained, when, by whone, etc. This is of interest when trying to assess data
reliability, and for data insertion.
Futher down the chain, Observation/result values will often be collated into "coverages"
in preparation for some analysis, anomaly or feature-detection, etc. But it is very much the case
that the structure of a "coverage" when expressed as a map of the range over the domain
is the same as the structure of a an observation which maps a result to a target.
See
https://www.seegrid.csiro.au/twiki/bin/view/Xmml/ObservationsAndMeasurements
for some detail.
Simon
