[Therion] A puzzle in Loch

[Bill Gee]

Hmmm.....   Maybe I am not using the splay flag correctly?  Is there 
another flag that might be more appropriate?

The reason those stations are flagged as splay is because they do not 
contribute to the length of the cave.  They are just connecting a side 
passage into the rest of the survey.  Marking the shots as splay means 
they get left out of the total length calculation.

That part of the cave is a big challenge to survey.  The main feature 
there is a stairwell with steel hand rails on either side.  The rails 
really mess with the compass measurements.  We tried every which way but 
could not get a good match between forward and backward compass.  I just 
have to trust that averaging the shots will get somewhere reasonably 
close to correct.

It also is a place where a lower level stream passage (the E series), a 
mid-level side passage (the BU series) and the main passage (plain 
numbers going up the stairs) all come together.

The survey trips in this part of the cave happened over three years.  We 
did not know the BU passage existed until someone was just fooling 
around climbing over a rail and along a rock shelf full of electric 
lights.  From the stairs it looks like a shallow alcove.  Even the tour 
guides who go past there multiple times every day had no idea.  Had we 
known, we would have left a good tie-in station.  As it is - we had to 
make due.

An extract from the centerline data file looks like this:

==========================
   data normal from to tape compass clino backcompass backclino left 
right up down

# Side passage behind the overlook
flags splay
# The next line is the data we actually shot.  Getting it to fit right 
on the map
# required juggling the numbers a bit, and that is the second line.
#  3      BU1     4.8     345.5    5.3    180.5   -6.3   - - - -
   3      BU1     4.0     315.5    5.3    135.5    -6.3   - - - -
   BU1    BU2    11.6      53.1   84.4    228.4   -84.9   16.8 2.2 1.1 11.6
flags not splay
   BU2    BU3    18.6     152.8    0.5    332.1   -0.7   4.6 0 0.5 5.1
   BU3    BU4    20.5     137.1   -1.1    318.1    1.4   10.7 6.8 1.0 2.2
   BU4    BU5    18.5      68.6    2.5    248.7   -2.3   4.9 1.9 1.0 0.8
   BU5    BU6    11.3     141.7   10.0    323.1  -11.1   0.5 10.6 7.2 2.3
   BU6    BU7     7.8     207.0   18.6     27.9  -19.6   12.9 4.4 18.2 2.8
   BU7    BU8     6.9     130.3  -48.0    312.4   47.8   3.8 3.7 5.9 0.5
   BU8    BU9     8.6     184.0   10.4      3.2   -9.8   6.4 2.6 3.4 3.0


===============
Bill Gee

On 8/15/23 17:10, Tarquin Wilton-Jones via Therion wrote:
> On 15/08/2023 22:52, Bill Gee wrote:
>> Looking at the .lox file for Stark Caverns, I see a spike that does not
>> make any sense.  I suspect it might be a blunder in the LRUD data,
>> perhaps a misplaced decimal point - but I have searched all over the
>> data and cannot find anything that looks out of line.  Besides, the
>> spike is not horizontal, which you would expect from an LRUD blunder. It
>> goes up at about a 20 degree angle.
>>
>> Take a look at the file at
>>
>> https://campercaver.net/MiscFiles/StarkCaverns.lox
> 
> Possibly unrelated to the problem, but ...
> Several legs are created with a splay, when it looks like they should
> have been a leg or a duplicate.
> BU1 to BU2 (where the problem is)
> G13 to Z1
> B1 to B1a
> AB1 and AB2
> A5 to R1
> 12 and 14
> These can cause issues, because splays are legs are different things,
> and you could confuse Therion when it tries to generate walls. It is
> supposed to use actual splays for that, but not duplicates. Because you
> are calling them splays, Therion tries to use them to work out where the
> walls are, and generates a wall where the LRUD data conflicts with what
> you have called a splay. So it tries to join the wall it drew at a
> station, with the wall you told it is somewhere else in the LRUD data. I
> can understand if it does so with a crazy spike, though it is usually
> better at handling inconsistent data.
> 
> I would need to see the source data to debug further, since I cannot see
> what any of the LRUD data looks like.
> 
> Cheers
> 
> Tarquin
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