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Re: [ferret_users] Direction of latitude in ferret

Hi Boyin,

The netCDF-CF conventions and virtually all mathematical analyses define latitude increasing from south to north.  Image processing conventions, which were to some degree adopted into GIS standards define the origin of an image at the upper left, instead of the lower left (a legacy of CRT sweep logic in the electronics of old ??).   Therein lies the conflict.

In Ferret you can use the /ORDER qualifier on the SET DATA command and the /VLIMITS qualifiers on the plotting commands to flip the direction of latitude if it is encoded in a reversed way from your needs.

    - Steve


On 6/29/2013 7:34 PM, Boyin Huang - NOAA Federal wrote:
Dear All,

I have a SST file (sst.nc) in NetCDF (v4.1.1) whose latitude starts from the North Pole (This is known by ncdump).

I listed the SST using the following:
use sst.nc
list/file=sst.dat/i=1:360/j=1:180/format=stream/clobber sst

I found that the latitude starts from the South Pole in sst.dat file rather
than from the North Pole.

Is this right, Does the Ferret automatically flip the direction of latitude?


Boyin Huang
Ingest and Analysis Branch
Global Climate Application Division
NCDC/NOAA, Room-514
Phone 828-271-4851
Fax 828-271-4022, 828-271-4246

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