What this hell is this and how to fix it?

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fobos8
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What this hell is this and how to fix it?

Post by fobos8 »

Hi all

I've been trying to register a project. The cloud to cloud stats say it's good but survey control says it's bad - 35mm bad. I'm 99.99% confident in my survey control, i put it in myself and I know it's good. I did a closed-loop traverse to an accuracy of 1 in 65,000.

In correspondence view it looks this below. From the "registered" point cloud to the crap surrounding it is 500 metres. When I processed the scans I limited them to 50meters.

Anyone seen this before?
messedUpProject.jpg
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Mike Annear
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Re: What this hell is this and how to fix it?

Post by Mike Annear »

I would have a look at the original scans for the " crap surrounding it at 500 metres". What sort of scanner are you using ?
Was there any windows or ponds or puddles in your scan area ? If not, it could be a problem with your scanner.
Try cleaning the "Crap" out of your original scans and then re-register it.
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Leandre Robitaille
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Re: What this hell is this and how to fix it?

Post by Leandre Robitaille »

If the scanner is not out of calibration. Mike has the best solution. Delete all the noise in 3d view, save, try the c2c registration again. Also when doing c2c registration make sure to spot check inclinometer missmatch(ctrl+enter on any selected scan), faro scanner has 0.015degree accuracy, use this info to evaluate if things are leveled or crooked.
fobos8
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Re: What this hell is this and how to fix it?

Post by fobos8 »

Mike Annear wrote: Sat Oct 24, 2020 12:35 am Try cleaning the "Crap" out of your original scans and then re-register it.
Leandre Robitaille wrote: Sat Oct 24, 2020 4:28 am Also when doing c2c registration make sure to spot check inclinometer missmatch(ctrl+enter on any selected scan), faro scanner has 0.015degree accuracy, use this info to evaluate if things are leveled or crooked.
Thanks for your comments guys.

The scanner is a Focus 150 plus. The crap which appears to be a long way away is in most scans. I deleted it (using a clipping box) and the cluster seems to register okay, not great but when I transform to survey control it's really bad, 50-100mm.

Some of the inclo mismatches are 0.1 and 0.2.

Yesterday I ran a test in a really clean environment, a 10m x 5m room. I put a checkerboard in the middle of each wall and scanned, rotated the scanner 180 degrees and scanned again. The registration was to 0.5mm and each scan placed the checkerboards within 0.5mm of each other.
...BUT the scanner said there was an SD card error and then said there was an internal error ( i think the error codes were 707 and 771).

Also when you view the scans in correspondence view there is a load of crap floating around. You really notice is a long way from the cluster 300-600 metres. There are no puddles in this room and I closed all the blinds of the windows.

I'm at a loss...
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Re: What this hell is this and how to fix it?

Post by INV_Scanning »

Hi Andrew,

looks like a multipath effect to me. Nothing to worry about.
To get rid of the stray aroung, just use the distance based filter and put it to a reasonable value (80 or hundred meters).

Regards Sebastian
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Re: What this hell is this and how to fix it?

Post by sim.herrod »

fobos8 wrote: Sat Oct 24, 2020 12:00 pm
Also when you view the scans in correspondence view there is a load of crap floating around. You really notice is a long way from the cluster 300-600 metres. There are no puddles in this room and I closed all the blinds of the windows.

I'm at a loss...
Obvious question but have you checked that the optics are all clean?
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Re: What this hell is this and how to fix it?

Post by Dave Andrews »

If you have enough survey control and you know it good; register without the inclinometer. If the scanner is not closing properly, it will show up during this process.
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fobos8
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Re: What this hell is this and how to fix it?

Post by fobos8 »

sim.herrod wrote: Sat Oct 24, 2020 2:30 pm Obvious question but have you checked that the optics are all clean?
Yes - seems okay. Would dirty optics cause all the crap to appear so far away from the scanner?

I just cleaned the optics - there was a slight mark. I did a test couple of scans and still there's loads of crap 300 - 600m away from the scanner
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Re: What this hell is this and how to fix it?

Post by sim.herrod »

fobos8 wrote: Sat Oct 24, 2020 3:27 pm Would dirty optics cause all the crap to appear so far away from the scanner?

I just cleaned the optics - there was a slight mark. I did a test couple of scans and still there's loads of crap 300 - 600m away from the scanner
It's happened to us before. From nowhere we had random 'noise' appeared in scans. Checked the optics and could see marks from dried rain drops. Cleaned it off and 'noise' disappeared.

At least you've ruled it out as a cause now.
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