[Therion] Loop closure

Bruce bruce at tomo.co.nz
Fri Jan 11 10:34:58 CET 2013

To phrase it differently to Martin, I think of it this way...

xvi files are outputs, generated by Therion, so they will change according
to changes in the survey network data, loop closures etc.

th2 files are inputs, created by the draughtsperson using Xtherion or using
a text editor. Even though the th2 file may reference xvi files, the th2
file is never changed by therion, so th2 files are never affected by
subsequent changes to the survey network.

There are probably many work flows, but the one I use assumes a constantly
evolving survey network.  Each survey trip has its own .th file(s), xvi
file(s) and .th2 file(s).  Each one is uniquely named and is never
substantially changed, even though subsequent discoveries and surveys will
alter the shape of the survey network and sometimes the drawing local to
some survey stations.  Of course if a new passage is discovered branching
off a previously surveyed passage, then the old th2 file will require a
minor edit to create a gap in the walls to accommodate the new passage.
Otherwise, the new survey and drawings are entirely described in a new set
of files. As an example my current project has about 120 sets of files for
about 20km of survey length.

-----Original Message-----
>1st question:
>How do you draw the walls from this new sidetunnel and connect it correctly
to the existing drawings?
>Do you work with the old .xvi or the new .xvi file?
>Do you use a new scrap and work with joins for the wall drawings?

To edit the old passage detail you will use the old th2 file, and it will
naturally already reference the old xvi file (not that it matters, as you
will look at the pdf output to see how the old and new match up, before
invoking a scrap join statement).

To draw the new passage you should create a new th2 file, and this will
reference the new xvi file (for the new passage only).

>2nd question:
>Now you do more survey at the end of the cave.
>In your .th2 file the old walls at there old positions.
Not relevant. The walls will generally still be in the same position
relative to the survey station.  Therions basic functionality sorts out the
morphing of the drawings to match the adjusted survey network.

>But with this loop closure from above the last station of the .xvi (first
of the new survey) is in a different position.
>Do you use the new .xvi file and draw the new walls in a new scrap and then
connect them with joins to the old survey?

Yes, each corresponding survey, xvi and drawing go together.  If you draw
carefully, you may not need to use join statements, although if there are
significant loop misclosures then joins are a good idea.


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