[Therion] Drawing the map of a vertical cave

[Tarquin Wilton-Jones]

Hi Jean-Florent,

> I am drawing the map of a cave that is so far mostly vertical. In the 
> map editor of xtherion is very hard to distinguish which lines / 
> stations of the xvi belong to which part of the cave, because they are 
> all drawn over each other when seen from above. When adding walls and 
> objects it becomes even worse.


In general, I can say "me too". We had this exact same issue. We kept 
our surveys short, so there were not too many stations overlapping. This 
was also important when gathering the data, though SexyTopo is actually 
very helpful there, and highlights the "current station" and its splays 
(this feature was added specifically because of our needs while 
surveying). I would dearly love something similar in XTherion...

This is part of our survey, where 10 passages overlap, within a vertical 
range of just 62 metres;
https://www.cavinguk.co.uk/pwlldwfn/pwlldwfnarticle/normal/Chaos.png
XTherion shows this as a grey jumbled mass of nonsense. Shorter surveys 
really, really helps to keep the noise down. However, it is often hard 
to find a convenient place to end a survey in a really vertical cave, 
and you end up giving yourself a load of ugly "join" commands to make up 
for it.

In these situations, XTherion seems to expect you to have drawn perfect 
lines in the cave, so you don't have to rely on the splays.

> Is there an easy way to deal with this? Maybe generating different xvi's 
> for the different levels in the cave and drawing the scraps in different 
> th2 files?


I don't worry about the drawn scraps, since they feel unimportant when 
not focused. I worry more about "which splay am I trying to touch with 
this line". We used Survex Aven to render the .3d output, click to focus 
a splay end, and repeatedly flick from plan (P) to elevation (E) to see 
the splays move, and work out which one ended up where in the plan view, 
then try to locate that same splay in XTherion. It was very helpful 
being able to have the two apps running on two screens at the same time, 
to compare them. Aven makes things a lot more easy to see. Loch does not 
have any useful splay focusing or keyboard shortcuts to help with that.

As for your proposal; sure, you can do that. Move the subset of the data 
into its own survey, create a .thconfig, select it, export an XVI. Use 
that in a .th2. But then you need to import your sketches and overlay 
them somehow to make it useful. And I don't know how to do that part. 
Maybe someone else here does?

I also note that exported XVIs use a much lower natural resolution than 
our surveying app's export. I think it might be possible to change that 
in the properties of the embedding command in the .th2, but again, I 
don't know how to do that.

Was that any better of an answer than shrugging my shoulders?
¯\_(ツ)_/¯

Cheers,

Tarquin