Converting splays from Therion into LRUDs for Survex

cavermark

New member
I've got some data that is Therion, which I need to convert into Survex (Yes, really, I do!).

The in cave data has been recorded as a series of splays at each station, without doing a set of LRUDs first.

Presumably if I create a set of LRUDs of zero length for each leg then cave converter would convert it to survex and show the splays...  but the cubes function wouldn't work...
I also wouldn't be able to print out plans with widths on ...

Any suggestions anyone?
 

kdxn

New member
Therion can export a Survex 3D model including splays.

Latest Cave converter now has an option to create LRUD data from a Survex 3D model with splay data.

Never tried this myself.........

 

Duncan Price

Active member
I did it the hard way by loading the Therion 3D model into Aven and then measuring the most appropriate LRUD at each station to create my own data set manually.  In many cases the splays bisected the centreline route and could be used directly (especially the UD element since surveyors often do vertical splays at each station).

I have used Cave Convertor to do the conversion and it doesn't make the most legible of SURVEX data files. YMMV
 

mulucaver

Member
Mark, I have a spreadsheet which will do what you want. Unfortunately it is on a computer 6,000 miles away. I could let you have a copy before the next expedition.
 

cavermark

New member
mulucaver said:
Mark, I have a spreadsheet which will do what you want. Unfortunately it is on a computer 6,000 miles away. I could let you have a copy before the next expedition.

I plan to avoid this problem on the next expedition  ;)
 

cavermark

New member
No.
I will politely request that anyone using Pocket Topo records LRUDs after every leg, before doing any splays.
Thus making the data as versatile as possible for the project.
:)
 

cavermark

New member
I would have to master the skills of teleportation to enter that cave, so I wouldn't be too worried about how I would survey it. 

I have other priorities before I try mastering teleportation (or Therion).

If we are saying your drawing is the bottom of a shaft - then the shaft would have had legs surveyed down it - so "traditional" LRUDs could be used. As to how many legs to use, I would probably use my fingers to count them:

:icon_321:

Most of the cave I want to get LRUDs for is in the form of passages, so can be surveyed in legs and LRUDs generated to give a reasonable representation of the shape (reasonable enough for most cave surveyors in the last few decades, anyway.)
 

sluka

New member
mulucaver said:
Which of these splay shots do you consider to be LRUD?

I'm sorry, but why LRUD? You may draw exact section with help of splay shots. LRUD is help in situations you have not real section. And it is not easy job according the Dave's picture :)
 

cavermark

New member
I want to use the Passage volumes function in Survex (splays are only shown as a line in survex).

Plus we a 205km cave system with LRUDs that Prof Pete Smart is using to study passage formation. It would be good to have the rest of the cave data in this area in the same format.
 

mulucaver

Member
cavermark said:
I would have to master the skills of teleportation to enter that cave, so I wouldn't be too worried about how I would survey it. 

I have other priorities before I try mastering teleportation (or Therion).

If we are saying your drawing is the bottom of a shaft - then the shaft would have had legs surveyed down it - so "traditional" LRUDs could be used. As to how many legs to use, I would probably use my fingers to count them:

:icon_321:

Most of the cave I want to get LRUDs for is in the form of passages, so can be surveyed in legs and LRUDs generated to give a reasonable representation of the shape (reasonable enough for most cave surveyors in the last few decades, anyway.)
I don't understand your reasoning. If you look at the name it's called cross section which is where you take your LRUD readings. What makes you think it's a shaft?
It's fairly typical passage shape with a rift hading up on the right, a notch on the left and a bit of a trench in the floor. The station is in a typical place on the wall.
I was going to write you a program to get the LRUD's from the splays but when I started thinking about it I realised it wasn't going to be simple. I try to make my LRUDs read the passage height you would show on an elevation and the width you would show on the plan but I know nothing about cubes in Survex so couldn't figure out what readings it would be expecting.
 

andrew

Member
Using lrud, gives very little indication of the cross sectional area, and therefore volume as it hardly relates. Easiest way to think about this is a rhombus (easier maths than ellipse) with the  diagonal lengths of 1 and 10. The area is 5 square units. When the diagonals are horizontal and vertical lrud gives 10 x 1 when the diagonals are at 45 degrees the lrud gives 10 cos 45 x 10 cos 45 = 50. That is a factor of between 2 and 10 out, without considering more complex shapes.
However, if the cross sections are drawn in therion, the program already needs to know the inside and out, it probably would not be difficult to write a program to calculate area. Another option is to use the lox model, which produces solid models with more information use, like the plan then from one of the exports I am sure a far better estimate of the true volume can be calculated.
On the idea of asking people using pocket topo to write down lrud, that seems a little unnecessary, a computer can do that back on the surface, although as I have hinted at above lrud is an idea that was used because it was the best we could do, however, it has been well superceded.
 

Rhys

Moderator
Perhaps in a world where everyone used Distoxes and Therion, then LRUD data has been superseded. However, we're not in that world - I'm not in it yet anyway! All methods for recording passage dimensions are an approximation and a fudge, of course. That's the nature of cave surveying. I wouldn't consider it unreasonable to ask surveyors who are adding to an existing data set to record data in a fashion that is compatible with the existing data - ie recording LRUDs in Mark's case.

Rhys
 

andrew

Member
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.
 

cavermark

New member
andrew said:
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 o_O o_O

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.
 

cavermark

New member
mulucaver said:
I don't understand your reasoning. If you look at the name it's called cross section which is where you take your LRUD readings. What makes you think it's a shaft?

I didn't spot the image name as I was sleep deprived and short of time this morning. The same reasons that I haven't got time to learn Therion.
 

cavermark

New member
andrew said:
On the idea of asking people using pocket topo to write down lrud, that seems a little unnecessary, a computer can do that back on the surface, although as I have hinted at above lrud is an idea that was used because it was the best we could do, however, it has been well superceded.

I was suggesting that in cave using distox and PDA they do the leg (3 shots), then shoot in the approximate directions of LRUD, then do whatever splays they want. 
As I understand it, Cave converter then deals with this to create LRUDs and "shade-in" the passage walls based on those, if you use the cube function. Other splays then appear as dotted lines on survex.
 

andrew

Member
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.
 
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