From: John Halleck (John.Halleck_at_utah.edu)
Date: Mon Feb 12 2001 - 00:15:14 CET
Received: (from mdom_at_localhost) by karto.ethz.ch (8.9.3/8.9.3/SuSE Linux 8.9.3-0.1) id AAA03331 for cavexml-outgoing; Mon, 12 Feb 2001 00:15:19 +0100 Received: from cor.oz.cc.utah.edu (nahaj_at_cor.oz.cc.utah.edu [155.99.2.2]) by karto.ethz.ch (8.9.3/8.9.3/SuSE Linux 8.9.3-0.1) with ESMTP id AAA03327 for <cavexml_at_cartography.ch>; Mon, 12 Feb 2001 00:15:18 +0100 Received: from localhost (nahaj_at_localhost) by cor.oz.cc.utah.edu (8.9.2/8.9.2) with ESMTP id QAA27979 for <cavexml_at_cartography.ch>; Sun, 11 Feb 2001 16:15:15 -0700 (MST) Date: Sun, 11 Feb 2001 16:15:14 -0700 (MST) From: John Halleck <John.Halleck_at_utah.edu> To: cavexml_at_cartography.ch Subject: Re: Other areas that haven't been discussed. In-Reply-To: <Pine.GSO.4.05.10102111518080.26377-100000_at_cor.oz.cc.utah.edu> Message-ID: <Pine.GSO.4.05.10102111605340.26377-100000@cor.oz.cc.utah.edu> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-cavexml_at_karto.baug.ethz.ch Precedence: bulk Reply-To: cavexml_at_cartography.ch
On Sun, 11 Feb 2001, John Halleck wrote:
> On Sat, 10 Feb 2001, Ralph Hartley wrote:
Before this gets too personal, I should should make something clear:
I don't object to your tag, I do object to what you claimed
should be done with it. The tag has it's uses. Your comments
about Zero Variance (formally the same as infinite weight)
are what I do object to.
The equivalent of zero variance can, and is, obtained in the
survey community in various ways, all of which don't involve
actual zero variances. (Since someone else in private email
asked: For example see Exercise 11.4 in Wolf and Ghilani's
"Adjustment Computations".)
If you have known bad data, then you have an idea of what
magnitude of error you have, and it is normally weighted
appropriately if it has to be kept in. (But, of course,
in contexts other than Cave Surveying it would often just
be commented out after it was reshot.)
> > Date: Sat, 10 Feb 2001 08:42:22 -0500
> > From: Ralph Hartley <hartley_at_aic.nrl.navy.mil>
> > Reply-To: cavexml_at_cartography.ch
> > To: cavexml_at_cartography.ch
> > Subject: Re: Other areas that haven't been discussed.
> >
> > > If a measurement is marked reliability="godgiven" any program should
> > > treat it as fixed, and apply no corrections, adjustments, etc. to it.
> > > Loop closures should consider its variance to be zero. It is the users
> [...]
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