id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
358	Expanded used of add_offset and scale_factor	arango	arango	"Expanded the update in src:ticket:356 to also include the '''scale_factor''' attribute.

Currently, all the NetCDF data input routines will check if any the following attributes: '''scale_factor''', '''add_offset''', or
'''_FillValue''' are present in the input NetCDF variable:

 * If the '''scale_value''' attribute is present, the data is multiplied by this factor after reading.
 * If the '''add_offset''' attribute is present, this value is added to the data after reading.
 * If both '''scale_factor''' and '''add_offset''' attributes are present, the data are first scaled before the offset is added. They are usually used for simple data compression.
 * If the '''_FillValue''' attribute is present, the data having this value is treated as missing and it is replaced with zero. This feature it is usually related with the land/sea masking.

Notice that the NetCDF attribute convention stipulates:

""When '''scale_factor''' and '''add_offset''' are used for packing, the associated variable (containing the packed data) is typically of type byte or short, whereas the unpacked values are intended to be of type '''float''' or '''double'''. The attributes '''scale_factor''' and '''add_offset''' should both be of the type intended for the unpacked data, e.g. '''float''' or '''double'''"".

On the other hand, the '''_FillValue''' must be of the same type as the NetCDF variable."	upgrade	closed	major	Release ROMS/TOMS 3.3	Nonlinear	3.3	Done