Laser Scanning 76km of NSW railway

Discussion in 'Miscellaneous & Oddities' started by Dr Tony, Apr 20, 2018.

  1. Dr Tony

    Dr Tony Full Member

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    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.
     
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  2. Dr Tony

    Dr Tony Full Member

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    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
     
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  3. SMR CHRIS

    SMR CHRIS Staff Member Moderator

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    Wow
    That’s a great bit of promo for your work interesting to see renderings and I’m sure this is just a small sample of what it can do.
     
  4. Andy_Sollis

    Andy_Sollis Full Member

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    I had a friend who works in vehicle crash scenes for the local police force scan my car to see if we could take the 3d scan they used and convert it to a 3d printed item (car) although the images were fantastic, we couldn't find a modelling system that would load and be able to use the 3d scan file as it was either the wrong file type, or if it loaded, the scan was simply billions of dot locations where it had reflected off. this also meant it left big holes inside the car (as it was a soft top too, where the angle of the camera had not picked up what it should (Mark had done it as per his normal work practice where he would do 4 or 5 external points around the crash) - we decided if we were to try again to add some extra ones in where the scanner would also pick up the interior... However, with me not having a program that could convert the file to be suitable to use on a 3d printer (.stl file) we gave up.

    12966591_10154200680407033_593003254_n.jpg
    This is not a drone photo, but actually the ground camera scans viewed from above. its amazing with the 3d scanner how much it captures. you can even see where we were stood at the time of the photos - my car is in the centre. (triumph Spitfire) - also note the Triumph TR7 top right.

    12968809_10154200680112033_1460949129_n.jpg

    Again looking from the other side. (empty works car park at a weekend.)

    was a clean up mark did for me of just the car.

    Its good,but unless your a big modelling company with hours and staff to throw at it, its not a simple thing to turn a 3d scan in to a 3d printed object.
     
  5. Dr Tony

    Dr Tony Full Member

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    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
     
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  6. Davoetype

    Davoetype Full Member

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    I think I will leave it to the experts......enough challenges on the layout already.

    Cheers

    and happy (simpler?) modelling
    'Richard
     

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