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Re: [ferret_users] Interpolation on co-range chart
Hi Dan,
For regular grids, the data should be on a modulo axis in longitude.
Then interpolation should also work in the right way as the axis is
correctly "wrapped" around the globe.
<http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/Grids-Regions/REGIONS#Chapter4-Modulo_axes>
When I had the same problem with single irregularly spaced data points,
I created a new variable shifted by 180 degrees in longitude. Then,
before interpolating, I tested the range longitudes and when it was
close to 360°/0°, then I interpolated on the new shifted variable
instead and subsequently shifted the result back by 180 degrees. That
was the easiest way for me to use the internal "set mode interpolate"
when dealing with single longitude values.
Cheers,
Hella
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*Subject:* [ferret_users] Interpolation on co-range chart
*Sent:* 2010-10-14 12:15:54 +0800
*From:* Yu, Hao-Cheng <danish.url@xxxxxxxxx>
*To:* ferret_users@xxxxxxxx
Dear ferret users,
I try to plot co-range chart with global tide data.
I notice ferret interpolated the values when the degree values across 360
(or 0).
For example, the region between 5 and 355, ferret will interpolate to 180.
(Should be 0)
This will cause lots of contour line in this region, and give wrong
interpolation values.
Is there anyone do such interpolation and avoid error like this?
Sincerely, dan
--
---------------------------------------------------------------
Hella Riede (Dipl.Chem.)
Max Planck Institute for Chemistry
Dept. of Atmospheric Chemistry
Becherweg 27 email: hella.riede@xxxxxxx
55128 Mainz phone: +49-6131-305437
Germany fax: +49-6131-305436
homepage: www.mpch-mainz.mpg.de/~riede
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