Marc Has suggested the ContextCapture.
Honestly I didn't know it was there . I'm going to download and play about.
But I suspect it using actual scanner positions as that's what ptx and e57 are in reality. So there is a central point and the plane is determined from central position (outwards) . 3d mesh creation is really complicated. The POD file you have I suspect is a cloud and has no scanner position information. The tunnels I have seen , are created with a trolley which scans a helix along the tunnel. But I accept I am probably wrong in this case.
The barrel method is a work around as mesh creation can only me made from one direction from above (Z) mostly. Lidar meshes and the like.
But the feature of draping in Descarte is cool. You can drape in a direction.
So put a path in the middle of the tunnel and spin your view round and keep draping around the tunnel wall.
Then you should have all the lines on the wall surface. Like a barrel.
Next Mesh of contours only the top half of the barrel as if you are placing a blanket on that side of the barrel . To create a roof of the tunnel.
Next use the lines(contours) of the bottom half of the tunnel and mesh contours.
This will be a basic tunnel but if its a long tunnel with lots of bends. Well as I said , 3d Mesh creation is complicated. Talk to the french.
I would honestly keep away from meshes for this job. Can be messy
Now I posted a link to that video and luckily it was a tunnel.
You basically create a line (path) of the tunnel. Then just draw what you see . It will be on that acs plane, perpendicular to the path you are following. You then just step through another step down the tunnel and draw what you see.
Once you give it a go, its actually really easy and surprising powerful. I'm using it to create objects in Aecosim at the moment and putting that in IFC BIM Models.
Steven
I hope Marc's not angry I mentioned the French