Converting splays from Therion into LRUDs for Survex

[mulucaver]

I did not say unreasonable, but why record anything that can be calculated after the event, in the warm with a drink in hand. Adding unnecessary jobs just increases the amount of work, leading to either less survey, or poor quality for the amount of cave time spent collecting it.
Modern data is compatible with the older stuff, it can be converted.

How to do this conversion is what I asked in the original post. Apparently it is not easy

My computer has just been thrown in the bin in frustration - I find it better to record the data in the way that it is needed in the cave, than rely on my non existent computer programming skills.

 

[Duncan Price]

Makes, sense, the splays should always be taken so lrud is available from them.

I am sure footleg will get round to it, but if not, I would be willing to help, footleg is probably more proficient.

To expand on my earlier post...

Andrew and I have been surveying Wookey 20 together.  He sent me the PocketTopo files that were generated and I coverted them manually into SURVEX format to mesh with the underwater data that was done using a centreline with SONAR readings for LRUD.  At most stations it was possible to use the splays to generate LRUD directly.  In complicated changes of direction, I was able to interpolate a suitable LRUD set from the splays.

I would add that I was operating the DistoX and (out of habit) tended to align some of the splays naturally along a line orthogonal to the centreline much like others have suggested.

It wasn't very difficult.  Just used a spreadsheet and opened up the .3d file in Aven to measure the odd distance when needed.

 

[andrew]

Quick play and topparser, just about produces lrud (well it does on a single test file but as a rule I make sure the first splays after a leg are equivelant to lrud.) Just  had not finished writing it as survex did not use to understand anonymous splay, it does now, I will aim to finish this for the new year. Will doing it from the .top files be okay, or does it have to be from the .th file (which will take writing a code to read therion files)

 

[mulucaver]

I did not say unreasonable, but why record anything that can be calculated after the event, in the warm with a drink in hand. Adding unnecessary jobs just increases the amount of work, leading to either less survey, or poor quality for the amount of cave time spent collecting it.
Modern data is compatible with the older stuff, it can be converted.

How to do this conversion is what I asked in the original post. Apparently it is not easy

My computer has just been thrown in the bin in frustration - I find it better to record the data in the way that it is needed in the cave, than rely on my non existent computer programming skills.

It is easy to do this conversion but you have to decide what you consider to be the criteria for the conversion, the overall height and width, the minimum height and width, the average height and width or whatever else you might have in mind, hence my original question.
For the benefit of this discussion I will post my PM reply to you.

What I?m getting at is this.
If cubes in Survex is based on the sum of  cross-sectional area at a station times the leg length then based on the LRUD readings being those bounded by the green rectangle will be very different to those of the red rectangle.
I?ve always used LRUD to define the extents of the passage shape as in the green rectangle where the height of the rectangle defines the ceiling and floor as shown in an elevation and the width defines the left and right walls as shown on the plan.

https://flic.kr/p/q2t8JH

Using the splay shots to define a series of triangles would be much better

https://flic.kr/p/pmTBPd

Sorry but I've not managed to put the sketches into the post, just links.

 

[mulucaver]

I would also say that the splays used when creating/calculating the triangles should be reasonably co-planar with the vertical plane within say 10 - 15 degrees.
And what do you do where there is a change in passage shape at the station. Have 2 stations close together?

 

[Duncan Price]

And what do you do where there is a change in passage shape at the station. Have 2 stations close together?

I have used two stations with a zero leg between them to accomodate for this - say a step in roof height or passage width.

 

[mulucaver]

The original purpose of LRUD readings was to enable the cartographer to draw the floor ceiling and walls in relation to the centreline. In the current discussion it is being used to calculate volumes. It was never intended for this and it just won't work for many reasons.

 

[cavermark]

The original purpose of LRUD readings was to enable the cartographer to draw the floor ceiling and walls in relation to the centreline. In the current discussion it is being used to calculate volumes. It was never intended for this and it just won't work for many reasons.

My main objective is to model approximate passage walls in Survex, to help with looking for connections, for which I am happy with the LRUDs as suggested by your green rectangles.


These are probably in keeping with the convention used for measuring LRUDs for most of the neighbouring caves, so we can compare like with like for relative trends for geomorphology, even if it's not the most accurate in absolute terms.

 

[mulucaver]

The original purpose of LRUD readings was to enable the cartographer to draw the floor ceiling and walls in relation to the centreline. In the current discussion it is being used to calculate volumes. It was never intended for this and it just won't work for many reasons.

My main objective is to model approximate passage walls in Survex, to help with looking for connections, for which I am happy with the LRUDs as suggested by your green rectangles.


These are probably in keeping with the convention used for measuring LRUDs for most of the neighbouring caves, so we can compare like with like for relative trends for geomorphology, even if it's not the most accurate in absolute terms.

I have a full 3d Loch model of Lagangs produced by Therion using all the splay shots (about 1000) and can easily do the same with Racer, in fact I already have one of Racer with the old data.