Changes between Version 11 and Version 12 of NetCDF_exportUpdateChanges

Timestamp:

Sep 21, 2011, 11:02:38 PM (13 years ago)

Author:

pds

Comment:

--

NetCDF_exportUpdateChanges

@@ -63 +63 @@
 However, there is certainly a use-case to export to a NetCDF file with no intention to access again via GDAL and use purely for use by CF-1 applications, in which case we don't need to save the added metadata.
 
+=== Add saving of Datum reference Ellipsoid parameters in CF-1 compliant format, in addition to within GDAL's WKT ===
+
+'''Related tix''': #2893 [[BR]]
+'''New -co options''': No, though related to the new proposed WRITEGDALTAGS option above.
+
+'''Has back-compat impact?''': No
+
+'''Change''':
+
+When exporting to NetCDF, save CF-1 attributes that specify the reference ellipsoid used by the projection SRS's datum. Continue also saving this information in the special GDAL "spatial_ref" tag.
+
+Note: when importing, the GDAL WKT datum information would be checked first as it fully specifies the datum. The CF-1 ellipsoid information would be usable as a fall-back.
+
+((?? pds: Should we add anything here about special import behaviour, e.g. whether to auto-detect datum on import based on ellipsoid values?? Or should there be an option for this?))
+
+'''Rationale''':
+
+CF-1 convention's only support of datums currently is to specify a reference ellipsoid using parameters such as 'semi_major_axis' and 'inverse_flattening'.
+
+While these attributes alone do not fully specify the datum (which requires an EPSG code so control points can be referenced), they at least allow fairly accurate map projection of the created NetCDF file using tools such as ncWMS.
+
+In the longer-term it would be beneficial to work with the CF-1 community to allow saving of full datum information in a format readable by CF-1.
+
 === When exporting to NetCDF map projections via GDAL, save projection coordinate variables. Optionally, also save lat and lon mapping variables. ===