Ignore specific message

[John Halleck]

On Tue, 28 Mar 2000, Andy Waddington on Survey stuff wrote:

> Date: Tue, 28 Mar 2000 12:46:05 BST
> From: Andy Waddington on Survey stuff <Survex@pennine.demon.co.uk>
> To: survex@survex.com
> Subject: re: Ignore specific message
> 
> Wookey discusses fixes to turn off "Fixed point not used" and/or "point
> already fixed" errors.

  My personal opinion, though nobody asked, is that the first is not
  intrinsicly an error, but a warning note that you should be able
  to choose or not.

  The second seems to be serious...  and I think I'm missing why 
  the data should have this problem.  (If someone could enlighten me
  [possibly by private email instead of the list] I'd appreciate it.]

  I think I much agree with what Andy Waddington wrote, which I'll mostly
  delete from this reply.

> I think there is a philosophy error in Survex (!).

  In recent conversation with Olly Betts, he made statements about possibly
  making the changes to the way fixed points were handled, since in this
  day of GPS you might have several GPS fixed points, and they have uncertainty
  that would have to be accounted for...

  So... I suspect that the discussion might become a lot more interesting
  when Olly gets back...

> [... Much Andy Waddington text removed ...]

> One workaround for the "fix not used" error is to add a zero-length survey
> leg to each fixed point - messy, but then it depends whether you are happier
> ignoring kludges in your data, or screeds of ignorable warnings. Ignoring
> warnings in transient output is not a problem, until there is a single error
> hidden somewhere in the great screed of warnings that scroll past.

  In the standard (Matrix, Normal) equations, it is possible to deal with
  multiple (weighted) fixed points rather trivally.   Since that is the
  matrix that the Cholesky Factorization in servex is being done on, I don't
  see why adding zero length survey legs would be usefull.  (Except for
  some explainitory purposes.)
  But if someone could explain this to me (possibly privately) I'd be
  willing to become educated.

> Andy

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> Survex http://lists.tartarus.org/mailman/listinfo/survex

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