On 7/14/2011 8:48 AM, Comiskey, Glenn wrote:
Hi,
The use of the variable unit value "degrees" would appear to discount
a data set from being both COARDS and CF compliant, at least according
to the CF conventions document, i.e. v1.5, section 3.1 states "The
COARDS convention prohibits the unit "degrees" altogether" while also
stating "this unit is not forbidden by the CF convention". Is this in
fact true?
The COARDS convention does indeed state, when refering to UDUNITS,
"names therein...will be regarded as acceptable unit names for this
standard with the following additions and deletions: "degrees" -
deleted". However, it then goes on to say "The unit "degrees" creates
ambiguities when attempting to differentiate longitude and latitude
coordinate variables; files must use "degrees_east"...and
"degrees_north"".
Is it not a case that the COARDS convention is disallowing the use of
the "degrees" value simply for coordinate variables, and subsequently
mandating the use of "degrees_east" and "degrees_north", to remove any
potential ambiguity with regards to the position the data relates,
i.e. COARDS requires "degrees_east" and "degrees_north" for
coordinates variables, but allows uses of "degrees" for a data
variable such wind direction (NOTE: I am aware that the CF standard
canonical unit is "degree").
Is there some convention (pun intended :-) to interpretating the
COARDS convention as meaning that "degrees" is prohibited, period?
Hi glenn:
"degrees" is a valid udunit for things like wind direction. It is not
allowed as a unit for lat or lon, period. I think that is how you are
interpreting it above.
john
Kind regards,
Glenn Comiskey
Data System Administrator
Fugro Global Environment & Ocean Sciences
Fugro House, Hithercroft Road
Wallingford, Oxfordshire OX10 9RB, UK
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(Direct) / Fax: +44 (0) 1491 820599
E-mail: _g.comiskey@geos.com_ <mailto:g.comiskey@g.comis...@geos.com>/
Website: _www.geos.com_ <http://www.geos.com/>
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