Laser Scanning 76km of NSW railway

Found myself with a bit of free time today and extracted my favourite type of portal for the overheads in the Blue Mountains. This is a normal double track portal with an extension for a relief line. These were alway intriguing for me as generally this relief line was rarely wired, despite the portal being designed to do so, and now, often the relief line has been removed, making these structures really stand out in their redundancy. For me, they are an essential part of the picture and one of my favourites.

Cheers
Tony

PS. 3D printing of these might work, but the strength could be the issue especially if they were to be "wired up". Portals are simple structures though, and should be quite easy to model using standard sections, just like the real thing.
The layout "Mullet Creek", which now resides at the shop of Australian Modeller, has portals made out of rail, not quite correct as not strictly beams, but they do a reasonably good job, even close up, and they would have the strength required.

 

My colleague put together a video explaining this whole project showing what was happening and a bit on how we did it, but mostly some really cool graphics and animations. This morning the manufacturer of the scanner, Riegl, published this video that we made, so I thought I would put it here too. There's no sound at first, but there is sound a bit later, some of the earlier versions of this we sped the footage up and imagined Benny Hill music, but we figured that would fall foul of quite a few copyright laws.
https://videopress.com/v/TAdPHjGN

 

Making models of things using a 3D scanner is a big part of my job. However, I am talking CAD model, or virtual model. What we do is scan a road, railway, building, industrial plant, sub-station etc and then use this data with a CAD program to vectorise the cloud. This requires considerable skill and experience of the operator (not trying to talk myself up here). There is no program that we have found that will reliably turn a series of dots in space (a point cloud, which is basically a file of the x,y and z coordinates of every point the scanner sees [plus reflectivity of that point]) into a series of planes and/or lines. We have tried a few, but it only takes a bit of noise (always inherent in current scanners, but also thing like passers by walking in front, even briefly) for the results to be very, very wrong.
There is software that can do this with aerial data from a scanner mounted in a plane, but the point density is vastly less for one. There are other factors here, but I won't go into them.
As you have seen with your scans, shadow is a big issue. When you are extracting manually, you can account for this by essentially "making stuff up", copying and mirroring surfaces that are repeated that might not be visible to the scanner. For example a pipe, you can see one side quite well, you know it's round, so you isolate that data and get the program to generate a cylinder that fits this data. Also a thing like a car would require a lot of scans and there comes a point where you can't scan it all.
The other big thing that you have found is the reflectivity of surfaces. Shiny things like cars are a disaster for current scanners. Along with glass, shiny metal and intentionally reflective things like road signs, the signal does all sorts of things, essentially leaving you with noise of one form or another.
The scanners prefer things like concrete, asphalt, wood and plastic. Non shiny metal is fine too.
Water is an issue as the water will absorb the laser energy, resulting in no signal return. So a partially wet object is going to be a problem.
We use Microstation with a point cloud processing plug-in for our work, this is big dollar stuff in the purchase and licensing. Most likely out of reach of any model railway company, even if your time using it was free.
Making a vector model of a Spitfire would be really challenging with all the complex curves in 3D. Even a boxy 80s car would be quite hard.
Good to have a go anyway and see what it can do.
Cheers
Tony