Print preview, LRUDs on vertical caves

[Mateusz Golicz]

On 07/03/2013 02:59 PM, Erin Lynch wrote:

> We have a number of large shafts where we've recorded passage dimensions
> along four different bearings (i.e. 045,225,315,135) instead of using standard LRUDs.
> It would be helpful if survex had an option to enter this sort of data

I would say this is highly related to constructing not tubes, but rather 
"bubbles" from a bunch of splay shots in arbitrary directions, as 
resulting from surveying using the paperless kit (distoX + PDA).

I can commit to code it (well, maybe not in a few days)... but I am at a 
loss in search for a reasonable algorithm to do the job.

I would prefer not to resort to heuristics like interpolating a 
cross-section at every station and joining these cross-sections into 
tubes (what about junctions, halls etc...). Instead I seek something 
universal, that would work reasonably well for LRUDs, readings such as 
yours (passagestation045225315135), as well as for a few dozen of splays 
from the paperless kit.

Simple convex hulls are not good enough, they behave oddly for plain 
LRUDs (ceiling, floor, walls wooble). I have considered building an 
union of convex hulls for each centerline shot (instead of each 
station), but that's still not perfect.

I have also played a bit with MeshLab, but I noticed that when 
computational geometry scientists say something on reconstructing 
volumes from "sparse sets", they mean point clouds of 100s or 1000s. And 
we have just a few per every station (4 - LRUD or maybe 10 - 20 in case 
of distoX).

I am writing all this in hope someone here can point me to some 
resources/ideas on this subject?

Except 3d modelling, what appeals to me is exporting such bubbles 
(tubes) into SVG together with contour data - in order to get halfway to 
a neat overview map of the area, similar to this: 
http://pliki.jaszczur.org/kongres-xy.pdf

Cheers!
Mateusz