[Therion] Joining surveys at a curved/sloping pitch

[Tarquin Wilton-Jones]

Hi all,

I have an awkward situation in my survey. One of our caves was surveyed
in 2 surveys. The 2 surveys join at a sloping pitch with a secondary
hole dropping into it.

I have managed to draw it all in a way that makes logical sense, but I
can't work out how to join the two surveys in the right manner. See
attached. Green = upper passage survey. Blue & purple = lower passage
and pitch survey. The part I want to fix is the green-blue boundary,
where the blue should ideally follow the "pit" lines

Ideally, pitches/pits should have their lower colour taken from the
lower passage, and their upper colour taken from the upper passage. This
is easy when they are in the same survey; you just draw your "pit" line
in the upper scrap, and then follow that exact same line with a
"-visibility off" wall in the lower scrap.

When joining surveys, they are joined in a straight line at the scrap
boundaries. This makes it very hard to draw the curved pitch heads,
since curves are not straight lines, and you cannot follow the exact
same line as the other scrap, because the other scrap sits in another
survey, in another .th2 file.

I can make additional "lower" scraps in the "upper survey" to follow the
pit outlines, but how can I make those scraps take on the colour of a
scrap using survey stations in another survey file?

Does anyone have any methods to work with this situation? (Preferably
not something that becomes just a bunch of trial and error, and then
joining every single curve point in the two surveys. I could do that,
but it is really painful.)

Thanks for any advice,

Tarquin
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