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Ticket  Resolution  Summary  Owner  Reporter 

#5  fixed  Forward old website to new website  halliday1  halliday1 
Description 


#8  fixed  Identifying horizontal coordinate variables using the axis attribute  cfconventions@…  jonathan 
Description 
1. TitleIdentifying horizontal coordinate variables using the axis attribute 2. ModeratorRuss Rew 3. RequirementA method is needed to identify which are the horizontal coordinate axes of a data variable 4. Initial Statement of Technical ProposalThe axis attribute of coordinate variables (1D, in the Unidata sense) is optional. The value axis="X" can be used on a longitude coordinate variable (CF 4.2), and axis="Y" on a latitude coordinate variable (CF 4.1) (caseinsensitive). CF is ambiguous about its use on other coordinate variables. The introduction of CF 4 states that the axis attribute is recommended for other kinds of spatial coordinate, but without giving an interpretation to its values. However in CF 4.1 and 4.2 it is prohibited for coordinate variables of rotated latitude and longitude. This proposal aims to clarify the use of the axis attribute for horizontal coordinate variables. The proposal is
5. BenefitsThe axis attribute, thus redefined, provides a clear way to identify horizontal coordinate variables and horizontal auxiliary coordinate variables. As an example, we can modify the one in CF 5.2: dimensions: xc = 128 ; yc = 64 ; lev = 18 ; variables: float T(lev,yc,xc) ; T:long_name = "temperature" ; T:units = "K" ; T:coordinates = "lon lat" ; float xc(xc) ; xc:axis="X"; xc:long_name = "xcoordinate in Cartesian system" ; xc:units = "m" ; float yc(yc) ; yc:axis="Y"; yc:long_name = "ycoordinate in Cartesian system" ; yc:units = "m" ; float lev(lev) ; lev:long_name = "pressure level" ; lev:units = "hPa" ; float lon(yc,xc) ; lon:long_name = "longitude" ; lon:units = "degrees_east" ; float lat(yc,xc) ; lat:long_name = "latitude" ; lat:units = "degrees_north" ; The axis attributes identify xc and yc as horizontal dimensions, and indicate that xcycup is righthanded. Because xc and yc are the dimensions of lon and lat, these auxiliary coordinate variables are also implied to be horizontal. In this case, we can also deduce that from the fact that they are identifiable as longitude and latitude, but for a general 2D coordinate variable it might not be obvious. There is no backward incompatibility because the redefinition permits the axis attribute in cases where it was formerly not allowed, but does not change its meaning in existing cases. 6. Status QuoWith the CF standard as it is, latitude and longitude coordinate variables can be identified by their units or standard_name, and they are well known to be horizontal. Other horizontal coordinate variables can be identified only by recognising specific standard_names e.g. those in Appendix F on map projections. The axis attribute is a more general solution that works without any knowledge of the possible choices of horizontal grid. 

#12  fixed  Formula terms for ocean_sigma_coordinate are incorrect  kyle  rsignell 
Description 
The format for the "ocean_sigma_coordinate" formula_terms attribute should be formula_terms = "sigma: var1 eta: var2 depth: var3" I checked the CFconventions 1.0 doc from 2004 and it's correct there, but even version 1.0 of the docbook http://cfpcmdi.llnl.gov/trac/browser/cfconventions/trunk/docbooksrc/appendixd.xml?rev=1 has it wrong, repeating instead the "ocean_s_coordinate" formula_terms. 