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Re: POLY_2D inconsitent interpolation [message #49704 is a reply to message #49687]

Fri, 11 August 2006 07:50

news.verizon.net
Messages: 47
Registered: August 2003

Member

R>
> Is this a well known bug? Do workarounds exist? I am especially
> interested in workarounds for hastrom, since this bug shift my sources
> by 1/2 a pixel relative to the astrometry in the header depending on the
> interpolation method used.

I think the bug is well known but only as it pertains to CONGRID for
which RSI added a CENTER keyword in 2001 after numerous complaints:

; CENTER: If this keyword is set, shift the interpolation so that
points
; in the input and output arrays are assumed to lie at the
midpoint
; of their coordinates rather than at their lower-left corner.

Examing the code for CONGRID one finds that use of the CENTER keyword
alters the input parameters to POLY_2D by 0.5 for the interpolation
cases but not for the nearest neighbor, just what was found was needed
in the original posting by Craig DeForest.

It sounds like a similar fix is needed to hastrom.pro in the IDL
Astronomy Library but I don't have time to do this today (but probably
within a week). --Wayne

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[Message index]

		POLY_2D inconsitent interpolation By: Randolf Klein on Mon, 07 August 2006 16:31
		Re: POLY_2D inconsitent interpolation By: news.verizon.net on Fri, 11 August 2006 07:50
		Re: POLY_2D inconsitent interpolation By: Randolf Klein on Fri, 11 August 2006 17:41

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