| Re: polar interpolation [message #33630 is a reply to message #33519] |
Mon, 13 January 2003 09:12   |
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Stein Vidar Hagfors H[2]
Messages: 28
Registered: October 2002
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Junior Member |
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James Kuyper <kuyper@saicmodis.com> writes:
> Thomas Gutzler wrote:
>>
>> Good morning,
>>
>> I am looking for a function that can do a polar interpolation of a
>> [2,n]-array.
>> What I don't want is to convert polar koordinates to rect, interpolate,
>> and reconvert them to polar.
>
> If you have data that comes close to the pole, that's precisely what you
> should do. Otherwise, you're going to see some very bizarre results in
> that vicinity. The pole is a singular point in that coordinate system,
> and you can only approach it by using a coordinate system where it isn't
> a singular point.
>
> If you don't come close to the pole, you should be able to use ordinary
> interpolation routines, treating rho, theta as if they were x and y.
> That won't produce exactly the right results, but anything that produces
> exactly the right results is going to be mathematically equivalent to
> converting back to rectangular coordinates.
Wouldn't it be better to do the interpolation close to the pole in a
rotated (i.e. translated) polar coordinate system? Tilt the polar axis
by 90 degrees, interpolate, tilt back?
--
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Stein Vidar Hagfors Haugan
ESA SOHO SOC/European Space Agency Science Operations Coordinator for SOHO
NASA Goddard Space Flight Center, Tel.: 1-301-286-9028
Mail Code 682.3, Bld. 26, Room G-1, Cell: 1-240-354-6066
Greenbelt, Maryland 20771, USA. Fax: 1-301-286-0264
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