This message came from the CF Trac system. Do not reply. Instead, enter your
comments in the CF Trac system at http://kitt.llnl.gov/trac/.
#107: CF Data Model 1.7
-----------------------------+------------------------------
Reporter: markh | Owner: cf-conventions@…
Type: task | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Resolution: | Keywords:
-----------------------------+------------------------------
\
\
\
\
\
\
Comment (by davidhassell):
Replying to [comment:56 biard]:
Hi Jim,
Thanks for the points. I'll try to clarify.
> I find the phrases "vertical coordinates which are not geolocated" and
"horizontal coordinates which are not geolocated" to be confusing. It
seems to me that the georeference construct is documenting the
geolocation, not creating it. In addition, latitude/longitude coordinate
systems must also be georeferenced. There are, in fact, differences
between the latitude/longitude coordinates defined by different coordinate
reference systems (CRSs). The geographic community has pretty much
unified on global latitude/longitude systems and ellipsoids in recent
times, but you can't make that assumption with older CRSs.
I think that the construct is neither documenting nor creating the
geolocation. The information needed to geolocate the domain is split -
some of it is contained by the coordinate constructs themselves (typically
by the standard name and units) and some of it is contained elsewhere
(typically by grid_mapping or formula_terms). It is this latter
information which we are encapsulating in the georeference construct.
> It is possible to define a projected CRS without reference to
latitude/longitude at all. It could be done with a Cartesian CRS such as
Earth Centered Fixed (ECF). All the ones I know of are layered on a
latitude/longitude CRS, but I don't think you should assume layering
implies that a latitude/longitude CRS has special status.
The geolocation construct does not prescribe what "geolocation" means.,
i.e. it doesn't necessarily mean latitude-longitude. It could mean
"height" or ECF, or anthing. The example "To specify the relationship
between horizontal coordinates which are not geolocated and a logitude-
latitude ..." is merely highlighting the common case arising from many CF-
netCDF grid_mappings.
All the best,
David
\
\
\
--
Ticket URL: <http://kitt.llnl.gov/trac/ticket/107#comment:58>
CF Metadata <http://kitt.llnl.gov/>
CF Metadata
This message came from the CF Trac system. To unsubscribe, without
unsubscribing to the regular cf-metadata list, send a message to
"[email protected]" with "unsubscribe cf-metadata" in the body of your
message.
