Faro Scene Registration - Need Help

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tushard
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Faro Scene Registration - Need Help

Post by tushard »

Hello!

Recently we have scanned the upper deck of LNG Ship. We have around 700 scans & all taken close to each other for Cloud-to-Cloud registration.
We match the scans in correspondence view & all scans appear to have matched correctly but when we update the Scan Manager, it shows either yellow or red but not green. Any specific reason for this error? & what might be the possible solution?

Software - Faro Scene 2019.2
Scan Resolution 1/8, Quality 4x
Distance between 2 scans - approximately 3 meters
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Re: Faro Scene Registration - Need Help

Post by pfirmsto »

tushard wrote: Fri May 10, 2024 11:07 am Hello!

Recently we have scanned the upper deck of LNG Ship. We have around 700 scans & all taken close to each other for Cloud-to-Cloud registration.
We match the scans in correspondence view & all scans appear to have matched correctly but when we update the Scan Manager, it shows either yellow or red but not green. Any specific reason for this error? & what might be the possible solution?

Software - Faro Scene 2019.2
Scan Resolution 1/8, Quality 4x
Distance between 2 scans - approximately 3 meters
Level compensator? Ship won't remain same level? Just a thought.
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Leandre Robitaille
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Re: Faro Scene Registration - Need Help

Post by Leandre Robitaille »

pfirmsto wrote: Fri May 10, 2024 11:34 am
tushard wrote: Fri May 10, 2024 11:07 am Hello!

Recently we have scanned the upper deck of LNG Ship. We have around 700 scans & all taken close to each other for Cloud-to-Cloud registration.
We match the scans in correspondence view & all scans appear to have matched correctly but when we update the Scan Manager, it shows either yellow or red but not green. Any specific reason for this error? & what might be the possible solution?

Software - Faro Scene 2019.2
Scan Resolution 1/8, Quality 4x
Distance between 2 scans - approximately 3 meters
Level compensator? Ship won't remain same level? Just a thought.
Its scene 2019, it doesnt use inclinometer data in c2c registration.

First 1/8 is low for c2c registration.
Second, you need to download scene 2023.1 and do a fine registration, its an improved c2c registration.
Add conections if your loops dont close (cant do that in 2019) and increase sample size, lower the bar to maybe 0.02

Also if its at shore, delete all and any points on the land next to the ship as that might move and affect c2c registration

You might need to QC inclinometer missmatch, turn most of them off if the ship was on water. Or you can lower their weight, maybe do a 5 for c2c and 0.01 for inclinometers
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Re: Faro Scene Registration - Need Help

Post by christopherbyrne18 »

I would not risk C2C for this type of work and especially with a Faro...

It needs to be properly controlled with targets & control to manage error propagation.

I'd also range gate every scan to 10-15m max as at medium to long range that data is too inaccurate.
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Re: Faro Scene Registration - Need Help

Post by tushard »

Unfortunately, we cannot use targets because of the time shortage available to do the job & that is also the reason we use 1/5 or 1/8 resolution.

I did keep the GPS & Altimeter on during C2C registration & the Scan Manager turned green but need to make sure the registration is correct by slicing the data at different positions.
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Re: Faro Scene Registration - Need Help

Post by Leandre Robitaille »

tushard wrote: Wed May 15, 2024 12:35 pm Unfortunately, we cannot use targets because of the time shortage available to do the job & that is also the reason we use 1/5 or 1/8 resolution.
You will get worst accuracy overall with very bad registration running 1/8 4x vs running 1/4 1X that is faster. Yes it is slightly more noisy but at least its well registered

GPS and altimeters are accurate to +-10m. They do not help in c2c only with top view based.

Plus I can run 3 scanners and spheres in most sites without loosing time, dont agree that targets is a time constraint, its just something lazy people say. However, I dont agree here that total station control points are needed, with proper scanning technique you can achieve in the +-5 to 10mm overall accuracy here

Btw even if you get "green light", using c2c in 2019 you will have a U effect, having vertical differences of up to 0.5m in a 300m distance.
Have a read here: https://www.laserscanningforum.com/foru ... 4&start=20
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Re: Faro Scene Registration - Need Help

Post by Tanguy Nédélec »

Hello,

You can check the help PDF, search for "traffic light". It says that the color indicates the quality of scan fits. In your "Scan Results" tabs, do you see one or more red-colored scans? If so, it means there's a bad link, that's where you need to investigate, by slicing the point cloud with a thin clipping box as you mentioned.
In my experience, Scene will try to match scans together that are rather far away with a bad overlap, throwing the registration off overall. With Scene 2019, there's not much you can do to correct this: try grouping scans in smaller clusters, or delete far-away points (use the distance filter in the processing tab for example).
As Leandre said, I strongly recommend updating to Scene 2023.1, where you can manually add or remove link between scans.

P.S. : altimeter and GPS have no effect on the relative position of scans. Doing the C2C again (even with the same parameters) can improve things however, that's probably why your scan manager turned green the second time.
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Re: Faro Scene Registration - Need Help

Post by landmeterbeuckx »

Leandre Robitaille wrote: Wed May 15, 2024 1:32 pm
tushard wrote: Wed May 15, 2024 12:35 pm Unfortunately, we cannot use targets because of the time shortage available to do the job & that is also the reason we use 1/5 or 1/8 resolution.
You will get worst accuracy overall with very bad registration running 1/8 4x vs running 1/4 1X that is faster. Yes it is slightly more noisy but at least its well registered

GPS and altimeters are accurate to +-10m. They do not help in c2c only with top view based.

Plus I can run 3 scanners and spheres in most sites without loosing time, dont agree that targets is a time constraint, its just something lazy people say. However, I dont agree here that total station control points are needed, with proper scanning technique you can achieve in the +-5 to 10mm overall accuracy here

Btw even if you get "green light", using c2c in 2019 you will have a U effect, having vertical differences of up to 0.5m in a 300m distance.
Have a read here: https://www.laserscanningforum.com/foru ... 4&start=20
How do you do that? 3 scanners with spheres.... how do you name your scans.

Runing more scanners would give me headaches to know if i scanned all....
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Re: Faro Scene Registration - Need Help

Post by Jamesrye »

It's been years since I last used SCENE, but it sounds like you've scanned close enough so that cloud alignment will work (so long as you range clip). It sounds like when you are updating the scan manager that somehow its looking at the inclinometer values and pulling it apart.

You could try registering in clusters and then pulling the clusters together.

I'm a Cyclone Core user, which is great at registering this sort of thing.
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Re: Faro Scene Registration - Need Help

Post by Justin Richards »

tushard wrote: Wed May 15, 2024 12:35 pm Unfortunately, we cannot use targets because of the time shortage available to do the job & that is also the reason we use 1/5 or 1/8 resolution.
If you're doing every 3 meters, even if you did every 2nd or 3rd scan at 1/4 depending on overlap, it would at least provide a better foundation for the 1/8 scans to tie into.

SCENE 2023.1 and the new workflow would also help a lot, especially when it comes to keeping in check when closing a loop.

To try and fix what you have with what you have, I would start by putting a thin clipping box through every axis and see if you can visually identify issues with the scan. If it looks good check scans manager....

So looking at my highest numbers, it appears to all be leading back to one scan, I check that scan first and see if there is anything that is causing a problem I should delete, there is not so I check the scans linking to it and I can see that they all have coverage on trees out in the distance.
01.JPG
I delete the trees from all the scans besides 11 an run registration again, the highest error is now halved (but in this case, it probably didn't do much to improve the quality of the as much as it did just lowering the registration numbers). If you see a scan thats connected to a scan it shouldn't, run a distance filter or delete far away points and rerun registration, save often
02.JPG
If it's not critical, you might have to make a spit somewhere where you are closing the loop, but if you do that I would still be upfront about if it comes to that.
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