[Therion] Breaking a loop at a specific station on extended elevation

[Stacho Mudrak]

Hi Bruce,

I have added

log extend

feature to thconfig. It should log the traversing sequence of extend
algorithm to therion.log file.

HTH, S.

On Thu, 14 Nov 2019 at 19:29, Bruce Mutton <bruce at tomo.co.nz> wrote:

> Thanks Stacho,
>
> I have had a look through my projects, and I don’t think I have ever used
> an ‘extend ignore station’ because of its unpredictable results (but I have
> used many ‘extend ignore leg’, which usually work as expected).  A quick
> check seems to indicate all my projects are unaffected by your latest
> update 094ac85fc5.
>
>
>
> Having a play with Tarquin’s example, it looks like an effect of ‘extend
> ignore station’ is to cause the map-connection break to occur at that
> station.  That is conceptually quite nice for users.  It seems to be
> consistent in that behaviour for the simple example, and is only
> ineffective if the station chosen is not in a loop (as you might expect). I
> did not test it where there is a pair of open branches though – that is a
> common scenario that should be checked.
>
>
>
> One more wish list for extend.  I would like a;
>
>
>
> debug extend
>
>
>
> statement.  This would enumerate in the log file the sequence of
> stations/legs that the extend algorithm is traversing.  In complex survey
> networks with many loops it can seem impossible to unravel a sensible
> extended centreline.  For example, if there are six survey branches coming
> into a single station, how do you isolate the particular leg that you
> want?  A textual debug might help find the answer.
>
>
>
> Bruce
>
>
>
>
>
> *From:* Therion <therion-bounces at speleo.sk> *On Behalf Of *Stacho Mudrak
> *Sent:* Friday, 15 November 2019 00:09
> *To:* List for Therion users <therion at speleo.sk>
> *Subject:* Re: [Therion] Breaking a loop at a specific station on
> extended elevation
>
>
>
> Normally,
>
>
>
> extend ignore 6
>
>
>
> should do the job. But there was a bug in the code, so it did not work as
> intended.
>
>
>
> It should be fixed now in the latest commit. If some of you have more
> complex entended elevation projects, could you please check, whether this
> change does not introduce new errors?
>
> The behaviour of "extend ignore <from> <to>" should not be affected.
>
>
>
> Thanks, S.
>
>
>
> On Sun, 10 Nov 2019 at 12:08, Tarquin Wilton-Jones via Therion <
> therion at speleo.sk> wrote:
>
> What can I say?!
>
> Bruce, that was some black magic. I don't quite understand why asking it
> to ignore a leg then changing your mind and asking it to draw it anyway,
> would cause it to then split it at the point you want. I wonder if I
> will be able to make sense out of that in future.
>
> What is makes me wonder is; why doesn't this exist?
> extend break 6
>
> This could cause a centreline "weakness", and prefer (but not mandate)
> breaking at that point. It would massively simplify this control, and be
> much more predictable.
>
> > try to change the line in your .th file from:
> >
> > extend ignore 6 5
> >
> > to:
> >
> > extend ignore 5 6
> >
> > There is no leg 6-5 in your data, but there is leg 5-6.
>
>
> This does not work. I assume that is because it is trying to extend the
> centreline from left to right, so it steps backwards through that oxbow
> (compared with the data). Or maybe I have not played with Bruce's
> solution enough...
>
> Cheers!
>
> Tarquin
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