[Therion] Entering survey sketch without walls

[Bill Gee]

Hello everyone -

Yesterday we started a survey project in an abandoned mine.  This is a 
room-and-pillar limestone mine all on one level.  The mine is claimed to 
cover 35 acres (about 14 hectares).  We ran centerline around part of 
the periphery for a bit over 3000 feet and came nowhere near to 
finishing.  There was no sketch because we were really looking to place 
some of the entrances.

The mine is a known hibernaculum for tri-color bats which will soon be 
on the endangered species list.  It is also an attractive nuisance. 
There have been several "lost person/out of light" rescues in there, and 
many drunken parties.

The mine is owned by a municipality.  Financial resources are in place 
to gate all entrances, probably during summer 2025 after the bats leave.

Looking forward, we ARE going to do a full cartographic map of this 
mine.  That leads to my question for this group.

When we start doing sketch, there will be many sections that have no 
outside wall at all.  There will be inside wall to define the pillars. 
Therion has a very strong dependency on walls.

How can sketch like this be used in Therion?

I would be very glad to have hints and tips from anyone who has done a 
survey like this.

Thanks!

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Bill Gee