Actually, I have found a way, but it is cheating, and not suitable for a real-life project.
Just start the sequence from the other end of the survey. Now I expect it is not possible to make a gap at station 2.
#set gap at station 7 by starting from station 11
extend start 11
extend left 11
extend ignore 7 8
extend right 2 10
extend right 10
processing extended elevation ...
START 11@extendedloop
LEFT 7@extendedloop
LEFT 6@extendedloop
LEFT 5@extendedloop
LEFT 4@extendedloop
LEFT 3@extendedloop
LEFT 2@extendedloop
RIGHT 10@extendedloop
RIGHT 9@extendedloop
RIGHT 8@extendedloop
RIGHT 7@extendedloop #gap here
BACK 9@extendedloop
BACK 10@extendedloop
BACK 2@extendedloop
LEFT 1@extendedloop
done
From: Therion <therion-bounces@speleo.sk> On Behalf Of Bruce Mutton
Sent: Tuesday, 7 July 2020 20:59
To: 'List for Therion users' <therion@speleo.sk>
Subject: Re: [Therion] Revisiting Breaking extended elevations on specific stations
OK, I give up I think. It might not be possible to break a loop at it’s closing end.
Tarquin’s example…
1 2 1 0 -10
2 3 1 0 -10
3 4 1 45 -10
4 5 1 45 -10
5 6 1 45 -10
6 7 1 90 -10
7 8 1.71 225 60
8 9 1 225 10
9 10 1 225 10
10 2 1.8 225 -32.2
7 11 1 90 -10
# set gap at station 2
extend start 1
extend ignore 2 10
extend left 8
processing extended elevation ...
START 1@extendedloop
RIGHT 2@extendedloop
RIGHT 3@extendedloop
RIGHT 4@extendedloop
RIGHT 5@extendedloop
RIGHT 6@extendedloop
RIGHT 7@extendedloop
RIGHT 11@extendedloop
BACK 7@extendedloop
LEFT 8@extendedloop
LEFT 9@extendedloop
LEFT 10@extendedloop
LEFT 2@extendedloop #gap here
done
Looking at therion.log transcript we can see that Therion traverses 1 2 3 4 5 6 7 11, then steps back to 7 before stepping to 8 9 10 2 and consequently leaving a gap between two 2s.
If we had a statement to tell Therion to step back beyond 7 to 2, and THEN start generating we might get 2 10 9 8 7 and leaving a gap between two 7s.
This would play havoc with my ‘extend ignore’ rules of thumb for predicting gap locations though. https://therion.speleo.sk/wiki/extend#summary_of_all_extend_options_for_survey_centrelines
Another solution might be for ‘extend right 2 10’ etc to be an implied ‘extend ignore’ for any other legs emanating from station 2. But that would break many existing extended elevations, so although more intuitive, lets cancel that idea!
Bruce
-----Original Message-----
From: Therion <therion-bounces@speleo.sk> On Behalf Of Tarquin Wilton-Jones via Therion
Sent: Tuesday, 7 July 2020 09:12
To: Therion <therion@speleo.sk>
Cc: Tarquin Wilton-Jones <tarquin.wilton-jones@ntlworld.com>
Subject: [Therion] Revisiting Breaking extended elevations on specific stations
Hi all,
I have a puzzle that comes from my old puzzle:
https://therion.speleo.sk/wiki/breakingextend
1 2 1 0 -10
2 3 1 0 -10
3 4 1 45 -10
4 5 1 45 -10
5 6 1 45 -10
6 7 1 90 -10
7 8 1.71 225 60
8 9 1 225 10
9 10 1 225 10
10 2 1.8 225 -32.2
7 11 1 90 -10
Imagine you want to break the loop at station 7, so that Therion shows
1-2-3-4-5-6-7-11 as a single line, then 2-10-9-8-7 as a branch off it.
The break should be at the end of the branch:
10-9-8-7
/
1-2-3-4-5-6-7-11
If you say "extend ignore 7" or "extend ignore 7 6" it will do this:
1-2-10-9-8-7-11
\
3-4-5-6-7
Breaks at the right station, but on the wrong branch.
You can do "extend ignore 8 7" to break at the wrong station on the right branch. If you use "extend ignore 7 11" it ignores you, and breaks at the natural point, leg 2-3.
Is it actually possible to break at station 7 along the 2-10-9-8-7 branch?
Cheers!
Tarquin
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