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From: Joe Keane <jgk@netcom.com>
Subject: Re: shifting the pole in spherical coords.
Message-ID: <jgkD28CIE.FoL@netcom.com>
Summary: Don't use asin.
Keywords: accurate
Sender: jgk@netcom.com (Joe Keane)
Organization: none
References: <3et338$g3k@saba.info.ucla.edu> <3eu5do$fgl@daphne.ecmwf.co.uk>
Date: Wed, 11 Jan 1995 07:22:55 GMT
Lines: 12
Xref: glinda.oz.cs.cmu.edu sci.math.num-analysis:18221 sci.image.processing:11832

In article <3eu5do$fgl@daphne.ecmwf.co.uk>
Mike Fisher <dai@ecmwf.int.uk> writes:
>Convert back to spherical coordinates:
>	theta = asin(zrot)
>	lambda = atan2(xrot,yrot)

This is correct, but for best accuracy you should use this formula:

	theta = atan2(zrot, hypot(xrot, yrot))

--
Joe Keane, amateur mathematician
