[Therion] Using 3d Scan Data To Create A Map

Thu Jun 20 12:43:53 CEST 2019

Those with their own LiDAR instrument will usually have access to
their LiDAR manufacturer Software and this often includes automated
rendering of man-made surfaces - results quality depend a lot on the
LiDAR resolution and accuracy. Natural surfaces such as caves are more
difficult for Point Cloud software to deal with automatically.

For the rest of us, you may wish to consider the following open source
software for Point Clouds:
MeshLab - lots of functionality, poor interface, I used this a decade
ago when there were few open source options
CloudCompare - nice interface, I have not used it for a while
ParaView - uses PCL (Point Cloud Library), PCL can be used direct
depending on your coding ability
PDAL - a library of point cloud tools, need to use something like QGIS
for results visualisation
Blender - more for 3D videographics
3DTK - 3D Toolkit, not familiar with

Other options are available.

Kevin Dixon

On Thu, Jun 20, 2019 at 9:36 AM Martin Sluka via Therion
<therion at speleo.sk> wrote:
>
> Isn’t it as call for nuclear aircraft carrier to kill a fly?
>
> Martin
>
> Odesláno z iPhonu
>
> 20. 6. 2019 v 9:33, Pavel Herich <herich at speleodd.sk>:
>
> > This software should do it:
> > https://geoslam.com/hub/
> > P.
> >
> >
> > Dňa 2019-06-20 09:26 Martin Sluka via Therion napísal(a):
> >> I’m curios if there is a software able to create  vector map outline
> >> from cloud data automatically.
> >> Martin
> >> Odesláno z iPhonu
> >> 19. 6. 2019 v 23:13, kevin dixon <geospatial3d at gmail.com>:
> >>> Nick,
> >>> I have both DistoX2 and LiDAR data for parts of the same cave.
> >>> All the LiDAR scans were registered to create a single model as normal
> >>> for LiDAR.
> >>> The individual scans were then decimated in the Point Cloud Software
> >>> using a suitable distance to nearest neighbour. I found Survex gets a
> >>> bit overwhelmed with millions of LiDAR data so you may have to
> >>> experiment with a suitable distance between adjacent LiDAR data. Each
> >>> decimated individual scan was then output to LibreOffice Calc and new
> >>> ranges, bearings and inclinations calculated to create single station
> >>> Survex files with lots of splays, now all orientated the same way.
> >>> Dummy traverse observations were created within Survex to link all the
> >>> LiDAR scan stations based upon the Point Cloud registration
> >>> coordinates and elevations of the scan stations.
> >>> I then manually matched the Survex output of the above LiDAR data to
> >>> some known DistoX2 observations or in your case, perhaps known show
> >>> cave outline. You can do this within Survex by having your non-LiDAR
> >>> data as another survey then using a Calibrate Compass figure (may
> >>> require up to +/-180degrees) within the LiDAR Survex data to change
> >>> the orientation so as to match the known and also setting one of the
> >>> LiDAR stations within the Dummy traverse observations to coordinates
> >>> and elevation that give a good fit with the known data. Several
> >>> iterations are needed with these.
> >>> Hope that is self explanatory.
> >>> Has worked for me - I have a DistoX2 Survex model with very detailed
> >>> LiDAR data in two large chambers - the resulting LOG file looks a bit
> >>> weird eg.
> >>>    1 8659-node.
> >>>    1 19071-node.
> >>>    1 21844-node.
> >>>    1 22774-node.
> >>>    1 23053-node.
> >>>    1 24470-node.
> >>>    1 25278-node.
> >>> As a side note, part of my project includes a Show Cave and I have not
> >>> had a problem with insitu metalwork there or on scaffolded sections of
> >>> the cave. I have always kept the DistoX2 well away from metalwork and
> >>> when the passage is narrow with metalwork, I have used an intermediate
> >>> station with DistoX2 observations to it only, never from it.
> >>> I have considered the use of turned angles to get through a serious
> >>> metaliferous section - the Leica DST360 could do this for you or a
> >>> small theodolite - use magnetic obs at each end to orientate it all.
> >>> Kevin Dixon
> >>>> On Wed, Jun 19, 2019 at 9:02 PM Nick Bairstow <Nick at pff.uk.com> wrote:
> >>>> Hi, Something a bit different for the clever people out there.
> >>>> I have been playing with some 3d scan data and have attempted to use it to create a Therion map.
> >>>> Firstly we put created an outline of the cave passage using point cloud software and exported as dxf.
> >>>> I turned the dxf into a background sketch and drew around it and could output a nice pdf of our cave. Also did a manual scaling. So far so good.
> >>>> I added a dummy station and gave it entrance coordinates, then exported as a KML model. When I open the output file Google Earth fly’s to the correct spot and shows a pin with the cave name but no cave.
> >>>> My question is , does this fail because we have no survey data, centreline etc and it is impossible to do this or am I missing something.
> >>>> As an alternative I can export to an esri shp file and run that though Qgis and get what I want but as I am going to attempt to combine the 3 scan data with a several normal disto surveys I would like to see Therion Kml output work if possible to save lots of messing around. (GIS makes my head hurt)
> >>>> On a side note using the point cloud software I can slice though the scan data on different planes and pick up lots of detail, rocks and boulders etc. Using the dxf/background image method I should be able to get a very accurate representation of the passage. I can hear you all saying what the hell is he doing that for when he could just survey the cave in the normal way! Well the cave is a show cave and absolutely rammed with metal walkways and cables. Disto tests showed wild inaccuracy’s so it was looking like the only viable option was going to be to use a Total Station device which we don’t have.  We then had a very kind offer to scan the cave, this has proved to be very interesting but drawing a normal map is a bit of a challenge although it seems not impossible.
> >>>> Any help would be appreciated.
> >>>> Nick
> >>>> _______________________________________________
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