Conflicting sphere target distances Faro Scene 2022.1

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lsf
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by lsf »

Does anyone mind sharing a couple of scans where each scan 'sees' at least 3 of the same spheres?
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by landmeterbeuckx »

lsf wrote: Thu Mar 23, 2023 5:19 pm Does anyone mind sharing a couple of scans where each scan 'sees' at least 3 of the same spheres?
I must say i admire your persistence in trying to solve or explain your matter but the accuracies of standard tls devices is only a few mm's so you're never going to get the results you want.

If you want high accuracies you should look at other scanners like Surphaser and combined with Laser Trackers instead of classic total station because there will always be an issue.

TLS with a Faro, Riegl, Z&F, Leica,.... isn't to be combined with cnc or other high precision tasks. All these devices produce noise that has an affect on the complete output.
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by lsf »

Thank you for your input!

I just want to exclude that my S70 scanner is not the issue here, therefore if someone can share their scan, then I can verify the 3D distances in each scan between same target spheres and see what the variance is. I am also planning to rent new targets so that I can exclude my targets is the issue.

At this point I can’t completely exclude that it is not the software sphere finder issue, because of cases when the software places the sphere in wrong place. Probably it is the combination of everything. I have learned a lot during this exercise which is great, just want to have a couple more conclusions.

I wonder what do Faro Focus S series users state as the precision in their contracts with their clients, what is the standard statement?
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by VXGrid »

Alright, here have some data:
4 raw FARO scans (I think it was a S70), with identical spheres
https://nextcloud.pointcab.de/s/c8DNcGs2K2N5gKe
Link will expire in a week.

Scan positions in green (except the origin which is pinkish), sphere positions in pink
Sphere diameter 145 mm
scanPos2SpherePos.jpg
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by christopherbyrne18 »

Faro specs quote 19" angualr accuracy and a 3D point accuracy at 10m of 3.5mm so these results are to be expected.
Faro Focus.jpg
Ranging error is largely irrelevant and should be ignored. Good to see Faro including 3D point accuracy. Until recently I believe Leica was the only one doing so.

My experience with the Focus is that data has to be range gated to 10 -15mm to achieve a decent registration for any kind of high accuracy work. Had all kinds of registration problems to control control because of this.

Which is why we use a P40 for any kind of accuracy dependent work. 8" angular accuracy, which I'm sure is still the inductry best and more than twice as accurate at 25m compared to a Focus. Faro's as fine for basic building surveys but wouldn't use it for high accuracy work.
P40.jpg
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by SAttaya »

christopherbyrne18 wrote: Fri Mar 24, 2023 9:32 am Faro specs quote 19" angualr accuracy and a 3D point accuracy at 10m of 3.5mm so these results are to be expected.

Faro Focus.jpg

Ranging error is largely irrelevant and should be ignored. Good to see Faro including 3D point accuracy. Until recently I believe Leica was the only one doing so.

My experience with the Focus is that data has to be range gated to 10 -15mm to achieve a decent registration for any kind of high accuracy work. Had all kinds of registration problems to control control because of this.

Which is why we use a P40 for any kind of accuracy dependent work. 8" angular accuracy, which I'm sure is still the inductry best and more than twice as accurate at 25m compared to a Focus. Faro's as fine for basic building surveys but wouldn't use it for high accuracy work.

P40.jpg
That spec sheet is for Focus Premium and he is using a S70.
I believe the Premium has better specs relative to the S series as reported by FARO.

If you want to know what your scanner (tripod,targets, complete system) can do, run a controlled test.
have targets at various ranges, say min to max you would use them and maybe 3-5 feet between them.
If you want to know outside results, run the test outside.
(In the case of FARO, you may want to hand target, instead of using the auto target find OR the push pin, i.e., select the part of the target
you want to use for calculating sphere centers.

Again, just my two cents.
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by christopherbyrne18 »

Same angular accuracy for both.

The variation seen in distances between spheres is down to measuremnt uncertainty most likely from its relaitvey poor angular accuracy.

Horses for courses.
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by lsf »

VXGrid wrote: Fri Mar 24, 2023 3:57 am Alright, here have some data:
4 raw FARO scans (I think it was a S70), with identical spheres
Thank you so much! This data has the same issue. Is it okay if I share some screenshots for the community?
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by lsf »

The summary is bothering:"
VXGrid Data Summary.png
The values are displayed in mm. The results at 6.2m distance are better than 2m distance. The red values are really concerning. I really thought that there might be some issue with my S70 or my targets, but this exercise does not confirm this.

What quality/precision do you guys state in your job contracts? 1cm?
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Last edited by lsf on Fri Mar 31, 2023 6:55 pm, edited 2 times in total.
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Re: Conflicting sphere target distances Faro Scene 2022.1

Post by SAttaya »

why are there two (2) "4" spheres?
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