Re: [ferret_users] ASCII read issues

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi,
Just a picky comment here. Ned's absolutely right about using NPOINTS to define your axes, but I'd just like to clarify how it operates here. Ferret uses single precision to read in the numbers you specify in the DEFINE AXIS command.  Once it has the values, it uses double precision to store the axis coordinates, to compute with axis coordinates, and to write them out to netCDF files.

-Ansley

On 10/21/2011 1:42 PM, E. D. (Ned) Cokelet wrote:

Sam, just a couple of quick commnets:  The first thing I'd try is to NOT specify the lat and lon increments, but instead use the NPOINTS paramater in the define axis command.  That's because ferret only uses single precision to do the math in setting up the axes, and that's only good to 7 sig. figs.  So a define axis command might look like this:

define axis/X=26.375W:56.584E/npoints=9955/unit=degree xlong

define axis/Y=41.5S:38.175N/npoints=9561/unit=degree ylat

See if that helps.  Then there might be, need to be, or not to be a branch cut at the prime meridian.  If so, you'd use the /mod parameter when defining the x axis.  

------------------------------------------------------------------------------------------

Edward D. (Ned) Cokelet, Ph.D. Oceanographer

NOAA/PMEL                         off:  (206) 526-6820

7600 Sand Point Way NE     fax: (206) 526-6485

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Edward.D.Cokelet@xxxxxxxx

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