[Therion] Fwd: Re: How to calculate the volume of a cave

[Ben Cooper]

Thanks Bill. Wow that’s quite a difference between the two techniques!

I know such volume calculations are just an estimate but it would be a lovely feature to have in Therion!  

Sent from my iPhone

> On 29 Jan 2022, at 11:41, Bill Gee <bgee at campercaver.net> wrote:
> 
> Hi Ben -
> 
> The data file I refer to is a Compass file containing centerline and LRUD data from the cave.  It is not from either Therion or Survex.
> 
> In this case the cave is very small, only 50 meters, and there are only 14 survey stations.  Retyping it into a Compass data file did not take long.
> 
> Compass and MeshLab do very different calculations to come up with volume.  For my cave Compass gives about 2900 cubic feet and MeshLab gives over 20,000 cubic feet (about 585 cubic meters).  Compass is doing a simple calculation based on polygons and using only centerline plus LRUD.  MeshLab is a much more complex calculation based on a 3D model of triangles.  Ultimately its calculation can be traces back to centerline, LRUD, walls, passage height objects and cross sections.  Therion uses all of that to build a .lox file which, through translations, becomes the MeshLab file.
> 
> ========
> Bill Gee
> 
> 
>> On Saturday, January 29, 2022 3:42:33 AM CST Ben Cooper wrote:
>> Hi Bill, Torsten,
>> What is that file; is it a standard output file from Therion or Survex?
>> Best regards
>> Ben
>> 
>> Sent from my iPhone
>> 
>>>> On 28 Jan 2022, at 12:57, Bill Gee <bgee at campercaver.net> wrote:
>>> 
>>> Ha!  Torsten, you are a magician.  Thanks!
>>> 
>>> That was indeed exactly how I calculated this.  I had completely forgotten about it.  Fortunately the data file still exists on my Windows virtual machine, and Compass produces the number I need to defend.  I now know how to reproduce the calculation.
>>> 
>>> Breathing a huge sigh of relief ...
>>> 
>>> ========
>>> Bill Gee
>>> 
>>> 
>>>> On Friday, January 28, 2022 6:40:00 AM CST Torsten Schnitter wrote:
>>>> Hi Bill
>>>> 
>>>> May be you are looking for this ... !?
>>>> 
>>>> cheers,
>>>> Torsten
>>>> 
>>>>> ---------- Ursprüngliche Nachricht ----------
>>>>> Von: Bill Gee <bgee at campercaver.net>
>>>>> An: therion at speleo.sk
>>>>> Datum: 14.08.2019 23:38
>>>>> Betreff: Re: [Therion] How to calculate the volume of a cave
>>>>> 
>>>>> 
>>>>> Update:  After poking around a bit, I discovered that Compass will calculate cave volume based on centerline and LRUD data.  Doing that means I have to run a Windows computer (ugh!) and type in the survey data twice (double ugh!)  Fortunately the cave for which I need this is small.