Dear All,
Reading this reminds me of an issue I need to address locally. We have units 'Degrees magnetic' and 'Degrees true' in our data system (many current meters are calibrated to magnetic and subsequently corrected to true). The local approach I am trying to take is to move the semantics to the parameter description (Standard Name 'equivalent'). However, I guess I'm not alone in needing to provide labels to data in both co-ordinate systems, so agreeing a policy on how this situation is handled in CF could be helpful.
Cheers, Roy.
________________________________
From: cf-metadata-bounces at cgd.ucar.edu [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Comiskey, Glenn [g.comiskey at geos.com]
Sent: 14 July 2011 15:48
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Units: degrees - COARDS/CF Convention
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?
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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E-mail: g.comiskey at geos.com<mailto:g.comiskey at g.comiskey_at_geos.com> / Website: www.geos.com<
http://www.geos.com/>
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Received on Sun Jul 17 2011 - 13:10:05 BST
