Hi Tim,
It may be I havn't understand well your question, but for the netcdf-c
library you van specify special attributes, that are been used to
specify the ourput format.
For example, in CDL, you can specify a global attribute
:_Format = "netCDF-4" ;
to the output as netCDF-4, or the the netCDF-4 classic format as:
:_Format = "netCDF-4 classic model" ;
if you add that special attribute to the CDL, the ncgen will generate it
in the specify format without using the -k option
$ ncgen -o file.nc file.cdl
Equivalent special attributes exists for chunking, deflating, shufling
andendianess
short z(time, number, level, latitude, longitude) ;
z:scale_factor = 4.97891138815559 ;
z:add_offset = 161839.010544306 ;
z:_FillValue = -32767s ;
z:missing_value = -32767s ;
z:units = "m**2 s**-2" ;
z:long_name = "Geopotential" ;
z:standard_name = "geopotential" ;
z:_Storage = "chunked" ;
z:_ChunkSizes = 1, 1, 2, 144, 144 ;
z:_DeflateLevel = 9 ;
z:_Endianness = "little" ;
The NcML would be similar but, as in the CDL case, it depends if the
library/package/tool been used it's aware about those special attributes.
Hope this help in some way.
Antonio S. Cofiño
On 19/07/17 08:51, Timothy Patterson wrote:
NcML and CDL are able to provide a human readable description of a particular
instance of a product but are not designed to describe a more generic product
format specification.
The format specification would need to handle elements with values only known
at runtime (dimensions, scaling and offset attributes, etc.), the NetCDF model
used, the underlying storage layer, aspects of chunking and compression, etc.
Basically everything you'd want to be able to construct NetCDF product
instances.
Having looked at a number of NetCDF format description documents, there doesn't
seem to be a standard way of describing a NetCDF format specification. In
general, the specification authors resort to either breaking the format into a
tabulated description or using a modified/annotated NcML or CDL.
Is there a preferred or standard way of describing NetCDF formats or has
anybody looked at developing something like a standard XML product
specification to do this?
Best regards,
Tim Patterson
_________________________________________________________________________________________
Dr. Tim Patterson
Instrument Data Simulation Expert
Product Engineering/Test Data Coordination
MTG Programme
GEO Division
EUMETSAT
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Tel: +49 6151 807 487
Fax: +49 6151 807 7
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