Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

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Augusto 3D
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Augusto 3D »

nyterydur wrote: Wed Jul 06, 2022 2:07 pm
maxwell566 wrote: Thu Jun 30, 2022 6:23 pm Scene,trw only allows me to georeference scans to survey control. there isnt a workflow to apply a transformation to the scans to re register them to the survey control ( as far as i can tell ) this would be ideal. Register the entire project cloud to cloud and then holding the survey control to adjust the entire scan as a whole to the survey control. i dont see that this exists anywhere.>
maxwell566, the way we incorporate survey control into Scene that was ran as c2c is:
1. We have a scans cluster containing all the scans properly placed and locked using c2c method
2. We create a Control cluster at the highest level and drag the scans cluster into it
3. We create a References folder within the Control cluster and import surveyed points or manually enter in points / checkerboard coordinates
4. Mark those same targets (points or checkerboards) in the individual scans they can be seen in
5. Rename the marked point to match exactly what that corresponding point is called as entered in the references folder
6. Run target based registration on the Control cluster, and select Force correspondence by manual target name

What step 6 does is it forces the program to only look for matching correspondence names and forces those correspondences, its just a clean way of doing it knowing that your reference point is not trying to refer to the wrong marked point for any reason.

but this isnt "stretching" the C2C cluster to fit the distances in the control network is it? - its just placing the cluster where it belongs.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by nyterydur »

Augusto 3D wrote: Thu Jul 14, 2022 2:43 pm

but this isnt "stretching" the C2C cluster to fit the distances in the control network is it? - its just placing the cluster where it belongs.
No, that is correct this is not "stretching" the scan point tensions, its merely taking the body of scan positions as it was put together and moving it as a whole best fit to the 4 or so reference points that we have designated. Keyword being best fit. To my knowledge there is no way to get Scene to "stretch" the scan point tensions within a locked registered cluster to spread the amount of error out over the distance instead of the other way around. If you have any insights on that method that would be helpful.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by landmeterbeuckx »

Scene will only try to fit something in measured control points.

It is by no means a geodetic package, nor doest it treat scans this way.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by TommyMaddox »

landmeterbeuckx wrote: Tue Aug 09, 2022 7:37 pm Scene will only try to fit something in measured control points.

It is by no means a geodetic package, nor doest it treat scans this way.
And for interior space control or plant site control, you don't want it to treat scans that way anyways.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Augusto 3D »

TommyMaddox wrote: Tue Aug 09, 2022 11:20 pm
landmeterbeuckx wrote: Tue Aug 09, 2022 7:37 pm Scene will only try to fit something in measured control points.

It is by no means a geodetic package, nor doest it treat scans this way.
And for interior space control or plant site control, you don't want it to treat scans that way anyways.
I am not 100% sure what it is that you are saying that you do not want, but regarless, if scene is unable to transform a cluster and "Scale it / transform it" dimensionally based on control points, what is the point of using control on the site?

I was told my someone (I dont remember if it was here or vie e-mail) that if the cluster is UNLOCKED, it will transform and scale or stretch to the control point..

Going back to the original idea, why bother surveying control points is the point cloud will not be transformed to the control constelation.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Leandre Robitaille »

Augusto 3D wrote: Wed Aug 10, 2022 2:03 am
TommyMaddox wrote: Tue Aug 09, 2022 11:20 pm
landmeterbeuckx wrote: Tue Aug 09, 2022 7:37 pm Scene will only try to fit something in measured control points.

It is by no means a geodetic package, nor doest it treat scans this way.
And for interior space control or plant site control, you don't want it to treat scans that way anyways.
I am not 100% sure what it is that you are saying that you do not want, but regarless, if scene is unable to transform a cluster and "Scale it / transform it" dimensionally based on control points, what is the point of using control on the site?

I was told my someone (I dont remember if it was here or vie e-mail) that if the cluster is UNLOCKED, it will transform and scale or stretch to the control point..

Going back to the original idea, why bother surveying control points is the point cloud will not be transformed to the control constelation.
You want to use a smart target placement. We use 12 per scanner minimum, some projects we run 40+ spheres.

C2C smartly for closing loops. Bring all the scans to a same level and launch a big massive TB registration. We do 2k+ scans projects monthly and those TB take 2 weeks to finish but ITS THE ONLY WAY to have scene mold to control points. If you want to complain to Faro that Cyclone or Trimble Realworks or every damn 3d scan softwares has all those fancy c2c features that scenes does not then share this thread of mine to Faro;

viewtopic.php?t=18954

Full disclosure, they dont give a damn about your feedback regarding this issue and this is one of the most painfull and underwhelming conversation you will have in your life.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Augusto 3D »

Hey man, sorry what does TB mean in your post above? I am not following that part.
Scene is great for some things, but I agree it lacks in other important aspects the more I learn about it.

Would you mind sharing a little bit about your workflow in scene then? Are you using survey control with scene or just placing spheres all over to get fast registration? 40+ spheres is a ton on spheres - what size are you using?
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Leandre Robitaille »

TB registration stands for Target Based registration.
In Scene Cloud2cloud does not mold to control points. Period. It does not even care about the inclinometer data. You could do a c2c of 1000 scans in a straight line of a road and it could not care less about control points. It would have errors in the meters if not more.
So basically only way to have error mold to control points in Scene is to do a TB registration. If you have a locked cluster it is not spreading error or molding to control points. Hence why we bring all scans (or individual clusters - this involves cluster for closing loops, random c2c specific scans for rooms or etc.) to the same cluster level.
Thing to understand and that is very hard to teach about scene is that directionnal scans will only mold to control points if they are on the same cluter level. DO NOT split them by level or etc. I have ALL scans in the very same cluster (including those specific closing loop clusters/etx) so that the whole project actually molds to the control points AND use the 19 sec compensator of the scanner.

We use flexi 145mm sphere for indoor scans and 200mm for outdoor scans.
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Augusto 3D »

Leandre Robitaille wrote: Wed Aug 10, 2022 4:42 am "Thing to understand and that is very hard to teach about scene is that directionnal scans will only mold to control points if they are on the same cluter level."
^what is a directional scan?


How did you figure out that the inclinometer is not used in C2C, this is good info to know and information that Faro should be putting out in their trainings.

When you say the above, what do you mean by directional scan?
I see people splitting their projects by levels - where each level is a project. I am not really a fan of that, never was. I rather cluster levels - but I see what you are saying. It would great if you would post or share a screen shot of one of your projects (tree)

TB - Target based - Oh man its late, sorry.
So to recap a little, if I have surveyed checkerboards and have laid out spheres, then I can load my CVS file with my control point run a TB registration, and scene will create a cluster using all the information and will spread the error / drift to fit into the control network ?
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Re: Controlling Accuracy of 3D laser Scans in a Large INTERIOR Space

Post by Leandre Robitaille »

Augusto 3D wrote: Wed Aug 10, 2022 4:52 am
Leandre Robitaille wrote: Wed Aug 10, 2022 4:42 am "Thing to understand and that is very hard to teach about scene is that directionnal scans will only mold to control points if they are on the same cluter level."
^what is a directional scan?
Scans that are part of the loop/traverse/network. Sometimes I do all the rooms in c2c in small cluster but keep the corridors and stairs on on the same level for the bigger target base registration.
Augusto 3D wrote: Wed Aug 10, 2022 4:52 am How did you figure out that the inclinometer is not used in C2C, this is good info to know and information that Faro should be putting out in their trainings.
Look at the inclinometer missmatches after a C2C and that can give you hints on what is happenening. Otherwise it has been discussed in the past many times that by ticking inclinometer when doing a c2c the average of all inclinometer is applied to the bundle only after the c2c registration is done, individual scans are not influenced by it, the whole thing is leveled after the assembly of the scans to the average value of all the inclinometers. It is not used to prevent any vertical drift. All considered 19 sec accuracy is not ideal this purpose but having ''some %'' of tension to it would be great obviously.
Augusto 3D wrote: Wed Aug 10, 2022 4:52 am I see people splitting their projects by levels - where each level is a project. I am not really a fan of that, never was. I rather cluster levels - but I see what you are saying. It would great if you would post or share a screen shot of one of your projects (tree)
It looks just like it sounds. I have small c2c clusters for small rooms/closing loops. Basically you force the links to the control points in the reference folder and relaunch that top level scan manager in a target base registration. Error will then spread to your control points.
https://imgur.com/a/FlDgNJR

If you want to test all this for yourself, do a survey with spheres and scan a road in a straight line. Do as long as you can, like 400m.
Then do a big c2c registration of all the scans and then register that cluster (by dropping it in another cluster) to your control points, try to have points in the middle / ends. Notice how high the tensions are with your control points and look at your inclinometer missmatches and think about the accuracy of those inclinometers and ask yourself if any of those number make sense.
Then break that c2c scan manager and now do instead a target based registration of that cluster, notice how well the control points now fit also notice your inclinometer missmatches are in much better ranges.
This involves cleaning your spheres before, we use a mix of the Taglabs extended toolbox and ATS quality manager for this.
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