Scene - target based registration - influence of inklinometer

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Scene - target based registration - influence of inklinometer

Post by jakubjon » Fri Sep 15, 2017 11:29 am

I have locked cluster of 30 scans and external references (5 points equally spread around object measured with GPS). What is the difference between only target base registration (no sensor used) and target based registration with inclinometer turned on. When I use GPS points only, I got residuals up to 2 cm which I considered as OK. In case of inklinometer was turned on I got much worse residuals up to 7 cm.
How does the adjustment handle inclinometer data of all scans in this case? Is attitude of the locked cluster some kind of average attitude of all scans?

This is just theoretical question. In this case it doesn't matter. I am just wondering how does it work.

Thanks Jakub

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Re: Scene - target based registration - influence of inklinometer

Post by 3DForensics » Fri Sep 15, 2017 3:45 pm

I believe that if you are telling Scene to not use the inclinometer data and to align the scans based on the GPS data, you should expect that Scene will try to balance the errors between the GPS data. However, if you choose to use the inclinometer, then this has much greater weight as the "true" vertical is known (certainly much better than GPS data, especially in elevation), so you get greater errors.

Having said that, it would be good to get some input from the more experienced Scene users in this area.



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Re: Scene - target based registration - influence of inklinometer

Post by jcoco3 » Sat Sep 16, 2017 5:16 pm

We spent more time than I want to admit figuring this out, and even after confirming these results multiple times with some willing individuals at Faro I still don't feel 100% confident that it is exactly as I describe.

Rule #1. Only external references can tilt a scan or scans(aside from doing this manually in correspondence view or via transformation dialog) from its original recorded inclination. So this means the inclinometer will always be preferred even if spheres or checkerboards that do not have external references would otherwise naturally influence the tilt of scan or scans. Scene will ignore that influence for the physical movement of the scans during registration, but may acknowledge and report the tensions in the registration report. Cloud to cloud should not tilt scans either.

So in your case the external references should be tilting the entire locked cluster to fit your control whether the inclinometer is on or off during registration. I would imagine that the cluster doesn't actually move between the two different approaches, but the reporting is different as you are adding the inclinometer data into the mix for more comparison.

Note: If you had the inclinometer off prior to the cluster's internal registration then totally different results after registering to your gps control should be expected.

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Re: Scene - target based registration - influence of inklinometer

Post by Scott » Sat Sep 16, 2017 6:46 pm

re: Jonathan's post: +1

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