Hi,
The COARDS covention mandates the use of the "positive" attribute for a
vertical axis that is not a unit of pressure, i.e. if using metres to
denote altitude. It further qualifies use of the "positive" attribute as
a means of discovering vertical coordinate variables, i.e. the
convention states "A vertical coordinate variable will be identifiable
by: units of pressure; or the presence of the positive attribute..."
Does this, therefore, restrict use of the "positive" attribute to
vertical coordinate variables only? NOTE: CF convention (v1.5, Appendix
A: Attributes, page 50) reports use of the "positive" attribute as
relating to coordinate data only.
I ask as I have a number of datasets in which the vertical coordinate
variable is present, named "altitude" albeit it represents sea level
with a value of 0 (zero), unit value of metres and has a declared
"positive" attribute of "up", but also contains tidal data reporting the
height of the water column above a pressure gauge and an attribute is
wanted to be added to denote that increasing values represent a greater
depth of water, i.e. "positive" is down. Would use of the "positive"
attribute for data variables interfere with the discovery of vertical
coordinates as defined by COARDS?
Kind regards,
Glenn Comiskey
Data System Administrator
Fugro Global Environment & Ocean Sciences
Fugro House, Hithercroft Road
Wallingford, Oxfordshire OX10 9RB, UK
Registration No: 2985431 / VAT No: GB 655475606
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Received on Mon Jul 18 2011 - 03:42:07 BST
