Scene Faro feature request, calculate closing seam offsets

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Leandre Robitaille
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Scene Faro feature request, calculate closing seam offsets

Post by Leandre Robitaille »

Hi Faro and LSF,

This is a request of mine that would save a lot of time and potentially correct errors while on site. I am currently working on a 500 scan project that was surveyed by one of our technician. I was having a hard time alligning his project and closing the loop. To my suprise I found a scan that the seam is not closing properly.
Seem.png
In short the technician didn't properly setup the tripod and I now have to look up all the seams for all the scans to see if any are not closing properly. What I would appreciate as a feature, is a report, that could be done upon preprocessing, that would calculate how well the seem is closing. This should be possible to evaluate due to the overlap the seam has in each scan. I could then evalluate if the scans is correct, even on site after a preprocess and redo the scan if any issue is found.

This site is 12h drive from our office location.

Some other scanners like the leica gives you a warning when the scanner moved, I am hoping for a solution from faro. I would be ok with a software solution that would tell you after a preprocess. Our technicians dont necessairily have the time to open each individual scans after the survey once at the hotel, but reading a report in the morning after preprocess and before leaving site or finishing survey would be a great feature. Even if it is for at the office to prevent headache after trying to allign a survey for hours.

Thank you,
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Re: Scene Faro feature request, calculate closing seam offsets

Post by sreed »

Hi Leandre,

Your concern is valid and your solution would be welcome. You should, however, view the potentially offensive seam in 3D view to confirm it is erroneous. We have experienced planar views that look bad but in reality the 3D data is valid.

Also, the issue of collimation error is well known and has been discussed on this forum. Have a look at some of those posts. It is possible for the data to be corrected after the scan but it must be done by Faro as far as i can tell. We fought like hell on a project only to find this colimation problem as the root of the problem.

Our new Faro S series has "on-site" calibration that ensures this problem doesn't resurface. Sounds like you may be due for a calibration.

Before the on-site calibration feature of the S series scanners, we developed a test to validate the seam error.

PM or email me if you want to discuss further,
-S.
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Re: Scene Faro feature request, calculate closing seam offsets

Post by Leandre Robitaille »

Hi Sreed,

Simply to add that these scans moved from a tripod leg moving in the gravel it was setup. This solution would be to evaluate the offsets from setup errors (wind, vibration, legs moving). I am aware about the angular compensation, it is a great feature and seems to recover some mis calibrations related errors, but that feature does not work from scans that actually moved on site.

This request would be to flag scans that physicaly moved on site.

Best regards :)
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Re: Scene Faro feature request, calculate closing seam offsets

Post by jcoco3 »

Leandre, Sorry to hear about the problem. As Scott said, many of us have experienced this too late, so I think you might be echoing a familiar cry.

I believe there is so sort of function within the scanner that is supposed to tell you when the scanner is moved during a scan, but I am not sure the sensitivity is set to a tolerance that covers the relatively small movement that creates a seam issue like you have. I will also add that I have had a similar concern about seam error when it is being corrected or "compensated" during import in the newer versions of Scene. While this compensation has been a wonderful addition to Scene, essentially washing out or improving upon relatively minor seam calibration errors, it can bury a small moment that occurred during a scan. This may create a situation in which you think you have a nice looking scan since the seam is almost flawless, but in fact you could have a large discontinuity elsewhere in the scan. I don't think it currently posses the ability to correct the movement error, just the seam and from our early sampling, with mixed but overall good results.

So as not to just complain about a problem, I will try to offer what I think could be a solution but to be honest I don't know if it is practical.

So lets say the scanner's inclinometer/compensator or whatever you want to call it takes a reading the moment after you tap start to see what the initial level state is then records it. It does the same after the scan, so you can at least compare those numbers. What if the scanner was continuously recording level at even a coarse frequency during the scan? So then you have initial state, ending state, and some data in between. Now all that is missing is your ability to access and examine that data prior to and after the import compensation. For all I know that information might already be available, but I don't know where to look for it.

Do you think that would help your situation? What about an initial import report that generated this info so you could sort through the lower quality readings? Or better yet, like you have described something on-site on the scanner that says, "hey you!" "Why did you let the tripod move during my scan?"

I don't know why that feature falls short here, but maybe it is more difficult to implement than we think. Maybe it is just a tweak to a setting that would bother you with a warning if even the slightest motion takes place during a scan, or perhaps a threshold setting the user could adjust. Maybe if we talk about it more then it will get some attention :lol:

For very high accuracy work I have even considered using a separate device (like a data logging inclinometer) to monitor levelness throughout a scan or create something like a microscope webcam recording a video of a bubble level attached to the scanner. While I could create something goofy like that, the easiest and perhaps goofier option would be to mount the scanner on top of a total station and use its compensator to do the work. I think I feel like you and that this could be in the scanner without additional cost or effort. Like I said before, that is just a gut feeling, and it could be much more difficult than I think it is.
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Re: Scene Faro feature request, calculate closing seam offsets

Post by Leandre Robitaille »

To add details on what I am requesting,

For exemple here is an example of a scan that clearly has an offset due to vibration and not calibration ;
vib.png
now notice in 3d the ''overlap'' the seem has;
offset.png
What I would appreciate is some kind of calculation done to flag if there is any distance offset between the seams, I would then manually inspect those scans to confirm and redo it on site if needed
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Re: Scene Faro feature request, calculate closing seam offsets

Post by landmeterbeuckx »

if a scan done with a riegl has done a movement it will indicate after the scan. Good feature.

With a faro you'll have to check before leaving but with 500 scans that's impossible.
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Leandre Robitaille
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Re: Scene Faro feature request, calculate closing seam offsets

Post by Leandre Robitaille »

HI jcoco3,

Those are some great ideas, I would also like if the faro did a dual inclinometer recording check, but I think the reason why faro has not yet implemented this feature is because the inclinometer is not accurate enough on the faro (+-0.015 degrees). It would however save those scans that would move by lets say 0.5+ degrees tough and would be at a minimum a great firmware update to have.

For anyone wondering if the S series already does this inclinometer offset check, no it does not, you could move a leg of the tripod mid scan to test this.

I have not yet seen anyone request this elsewhere on the forum and tought it would be great to talk about this with the lsf community

Best regards,
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Re: Scene Faro feature request, calculate closing seam offsets

Post by landmeterbeuckx »

can't you just install a movement sensor on the tripod. I don't know any specific but there are bound to be solutions out there
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Re: Scene Faro feature request, calculate closing seam offsets

Post by Leandre Robitaille »

Hi landmeterbeuckx, I don't think there currently exist a solution for this besides switching to trimble or leica scanners or riegl

To add on even more on why this is an issue for faro scanners, you litterally can not inspect the scans after the survey before leaving the site. Before you can view a scan in a clipping box, you have to do the preprocessing first and on site it is not always a possible workflow. You can view the quick view but it is not always visible on the black and white image that there is an offset. Then in the morning (or late at night) after the preprocess is done, it is not always possible time wise to manually inspect all the scans.
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Re: Scene Faro feature request, calculate closing seam offsets

Post by jedfrechette »

jcoco3 wrote: Mon Jan 13, 2020 4:59 pmI will also add that I have had a similar concern about seam error when it is being corrected or "compensated" during import in the newer versions of Scene. While this compensation has been a wonderful addition to Scene, essentially washing out or improving upon relatively minor seam calibration errors, it can bury a small moment that occurred during a scan. This may create a situation in which you think you have a nice looking scan since the seam is almost flawless, but in fact you could have a large discontinuity elsewhere in the scan. I don't think it currently posses the ability to correct the movement error, just the seam and from our early sampling, with mixed but overall good results.
I completely agree, and this has been my concern from the very beginning when Faro decided to "fix" their collimation issues using the rather simplistic per-scan approach that they decided on.

The way I would like to see this handled is as follow:
  1. Scene estimates the collimation error for every scan in a project based on seam overlap.
  2. All scans should have very similar collimation errors, so apply the median collimation correction to all scans. Bonus points if you track collimation error across projects by scanner serial number so we can see how it is changing over time.
  3. After correcting collimation error, any remaining error that exceeds some threshold is likely a blunder (e.g. the tripod moved) and the user needs to know about it.
The results of all of the above need to be accessible to the user. I don't think any of this is difficult, it's just basic statistics.

Of course, none of the above protects you from a tripod that slipped on site, but at least you would be able to easily identify the problem once back in the office and that can save a lot of time.
Jed
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