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Re: Strange floating-point precision behavior [message #34010 is a reply to message #33926]

Mon, 10 February 2003 19:57

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

James Kuyper <kuyper@saicmodis.com> writes:

>
> Are you sure those are ECI coordinates? Interpreted as ECR
> (Earth-Centered Rotating) coordinates, they correspond pretty closely to
> Boulder CO. Interpreted as ECI coordinates, you'd need a fourth value,
> the precise time at which the conversion from ECI to ECR should occur.
> ECI and ECR coordinates match only once each day, so it would be quite a
> coincidence if those ECI coordinates happened to match the ECR
> coordinates for Boulder.

And, if 12 cm precision is really desired, then earth precession,
nutation, and polar wander are of concern, in which case, ECI and ECR
match each other... pretty much never! :-)

Craig

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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Strange floating-point precision behavior By: lloyd on Sat, 08 February 2003 15:33
		Re: Strange floating-point precision behavior By: tim on Tue, 11 February 2003 09:49
		Re: Strange floating-point precision behavior By: Craig Markwardt on Mon, 10 February 2003 19:57
		Re: Strange floating-point precision behavior By: James Kuyper on Mon, 10 February 2003 12:44

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