On 20/12/2019 20:58, Tarquin Wilton-Jones via Therion wrote:
If extend algorithm follows stations in order 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 and you specify extend vertical 3 extend right 8 Then stations 3,4,5,6,7 should be placed vertical and 8,9 on the right. I have tested it and in my example, it works like this.
In the case of what you said, I would have expected the following legs to be default (right):
1-2 2-3
the following legs to be vertical:
3-4 4-5 5-6 6-7 7-8
then the following legs to be right:
8-9
Instead, leg 2-3 will be vertical, and leg 7-8 will be right.
At least in my head, "extend vertical 3" feels like it should mean "everything from station 3 onwards". I think Bruce also expected this, given what he wrote in the wiki "extend" article: https://therion.speleo.sk/wiki/extend "Usually this option will not work as described, unless it is preceded by one or two extend right <leg> statements."
So perhaps this is either a generic misunderstanding; Therion assumes that by <station> it means <the leg that goes *to* the station>. We assume that by <station> it should be <the legs that come *after* this station>.
I don't know which of those is right. I have also never used this with Survex, so I don't know if Survex agrees with Therion - Perhaps Wookey can say?
Survex agrees with me. Therion does not. 1 2 20 0 -80 2 3 5 62 -10 3 4 5 12 -15 4 5 5 132 17 5 6 5 18 -15 6 7 5 201 -7 7 8 5 63 -10 8 9 20 0 -80 9 10 5 15 -45 10 11 5 357 -30 11 12 5 27 -25 12 13 5 290 -18 13 14 5 323 -22 14 15 5 300 -7 15 16 5 15 -35 16 17 5 337 -42 17 18 5 281 -38 18 19 5 225 -20 19 20 20 0 -80 Therion: extend start 1 extend left 3 extend right 8 export map -proj extended -o "somepitches.pdf" Survex specfile: *start somepitches.1 *eleft somepitches.3 *eright somepitches.8 extend.exe --specfile=extend.svx somepitches.3d somepitches_extended.3d I have attached the two outputs. You can see that they are not the same.