On 3/20/2013 6:47 AM, rhorne@xxxxxxxxxxxxxxxxx wrote:
Folks:
Last year we (GOES-R Ground System) proposed a change that would allow
coordinate variables to use scale_factor and add_offset (see trac item
#86 with title "Allow coordinate variables to be scaled integers").
We will be producing one type of product on a lat/lon grid and would
like to used scale_factor and add_offset with the coordinate variables.
One of these products spans the 180 degrees_east longitude (i.e. -180
degrees_east longitude) line.The implication being that the software
resolving the scale factor and additive offset needs to be cognizant
of the longitude coordinate variable "units".
Is this an issue ?
very respectfully,
randy
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Hi Randy:
Once #86 is approved (which i see as a clarification) then scale/offset
is fine.
An important consideration is that the coordinate values be monotonic. I
would recommend that you make them really monotonic, and not constrain
the values to lie between +-180 or 0-360. So if you cross the longitude
seam, just keep going:
179, 180, 181, 182 ...
or
358, 359, 360, 361, 362...
Really, this issue is independent of scale/offset. One applies the
scale/offset to get the values in the units specified, then you start
thinking about the semantics.
So I dont think its the case that the "software resolving the scale
factor and additive offset needs to be cognizant of the longitude
coordinate variable "units"."
John