BLK 360 Calibration Issue

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James Hall
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BLK 360 Calibration Issue

Post by James Hall » Wed Aug 08, 2018 6:04 pm

I have a Job that we scanned with the BLK 360 and the C-10. We are modeling structural steel members for this project.
The Registration work was done in Cyclone.
The C-10 data was registered to itself cloud to cloud and set to 3 control points. The control points where collected with RTK GPS and a level run was done. Some fly points where set with a total station inside the structure.
Our C-10 Data checked fine with our GPS points and total station.

With the BLK being small and lightweight, I thought it would be a good choice to put on our extending tripod and get scans of the top of the steel.
I limited the individual scans to 30 feet inside of each control space to limit the accuracy loss at 30 feet to 90 feet with the BLK scanner.
The BLK 360 data was registered to itself cloud to cloud and the residuals looked good. I then tried some cloud to cloud constraints between the two data sets and noticed significant misalignment issues. I then measured the same piece of steel at several points in the C-10 Data and BLK data. At 3 feet to the BLK scanner the height of the steel was different from the C-10 data by 0.50 inch and at 8 feet it was 0.25 inch different.
The data started to be comparable at about 12 feet.

I need to gather some more details then I'll be calling Leica to work out what is going on.

Has anyone compared the scans of the BLK 360 to real world objects or found any similar issues with their scanner?

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Re: BLK 360 Calibration Issue

Post by Felix_the_Cat » Wed Aug 08, 2018 6:51 pm

I have.

I have not found a root cause.

Some of it in my case can be attributed to the floppy tripod sagging during scanning. However, you were using a elevating tripod.

But I am convinced it just makes bad scans sometimes.

A question - if it's up in the air how are you starting the scan? We used a Faro up high and even after waiting five minutes and remote starting there was still a lot of sway. I don't use the tablet, so I don't know if you can remote start it like that.

It is NOT a unit for accuracy. I treat it like geoslam data that just happens to look really good.

Not a production ready unit by any means.

Good luck Brother, I hope it's something simple


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Re: BLK 360 Calibration Issue

Post by Felix_the_Cat » Wed Aug 08, 2018 6:52 pm

I have.

I have not found a root cause.

Some of it in my case can be attributed to the floppy tripod sagging during scanning. However, you were using a elevating tripod.

But I am convinced it just makes bad scans sometimes.

A question - if it's up in the air how are you starting the scan? We used a Faro up high and even after waiting five minutes and remote starting there was still a lot of sway. I don't use the tablet, so I don't know if you can remote start it like that.

It is NOT a unit for accuracy. I treat it like geoslam data that just happens to look really good.

Not a production ready unit by any means.

Good luck Brother, I hope it's something simple


Sent from my iPhone using Tapatalk

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Re: BLK 360 Calibration Issue

Post by James Hall » Wed Aug 08, 2018 8:45 pm

The BLK360 was started remotely with the iPad running Recap. I waited 6 or so minutes for our heavy duty Nedo elevating tripod to stabilize.
My steel beam measurements were from top of to bottom of flange. Seeing the point cloud version of the Beam shrink like in a perspective drawing was unsettling.

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Re: BLK 360 Calibration Issue

Post by Rikore » Wed Aug 08, 2018 9:29 pm

One of the big issues is the C-10 is a survey grade laser scanner and the BLK 360 is just an imager and not survey grade. The sway of the elevated tripod will also be an issue. May have been better to climb up and set the BLK on the beam for steadiness.

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Re: BLK 360 Calibration Issue

Post by Phill » Thu Aug 09, 2018 12:04 pm

James

Can we see some pictures?

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Re: BLK 360 Calibration Issue

Post by James Hall » Thu Aug 09, 2018 3:04 pm

Phill wrote:
Thu Aug 09, 2018 12:04 pm
James

Can we see some pictures?
Yes, Here is the BLK360 data. The measurements are picked from the cloud so not as accurate as the modeled steel would be. It still shows the variation on the sections.
I'll post the C-10 Data this afternoon for comparison.

The steel double angle assemblies all have contestant heights in the C-10 data.

James
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Last edited by James Hall on Thu Aug 09, 2018 3:06 pm, edited 1 time in total.

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James Hall
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Re: BLK 360 Calibration Issue

Post by James Hall » Thu Aug 09, 2018 3:24 pm

Rikore wrote:
Wed Aug 08, 2018 9:29 pm
One of the big issues is the C-10 is a survey grade laser scanner and the BLK 360 is just an imager and not survey grade. The sway of the elevated tripod will also be an issue. May have been better to climb up and set the BLK on the beam for steadiness.
We did scans on the ground with the BLK360 on a survey tripod as well with the same effects.
The C-10 data has enough coverage to complete the job and The BLK360 was manly for reference pictures.
I was disappointed that the BLK360 scans were poor.

James,

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James Hall
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Re: BLK 360 Calibration Issue

Post by James Hall » Thu Aug 09, 2018 8:15 pm

James Hall wrote:
Thu Aug 09, 2018 3:04 pm
Phill wrote:
Thu Aug 09, 2018 12:04 pm
James

Can we see some pictures?
Yes, Here is the BLK360 data. The measurements are picked from the cloud so not as accurate as the modeled steel would be. It still shows the variation on the sections.
I'll post the C-10 Data this afternoon for comparison.

The steel double angle assemblies all have contestant heights in the C-10 data.

James
BLK360 Steel beam test 1.jpg
Here is the C-10 Data which matches your steel sizes in our library file.
BLK360 Steel beam test 2.jpg
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Re: BLK 360 Calibration Issue

Post by Phill » Thu Aug 09, 2018 10:27 pm

James

I cant see the measurements in those photos. Are you saying that the scanner is changing the distance the further from the scanner you get (kind of like a scale factor), or is it the beam is not level. You seem to indicate it is bending the beam when it should be straight? Is that correct? And this only happen out to a certain distance, after which if comes good. If it was me I'd be getting the targets out, putting the BLK side by side with the C10 and place targets out at series of distances from the two scanners.

Can you place a beam in the two scans aligned to the cloud and then show the centre of the beam in orthogonal view, so we can see the deviation.

The other point here (to do with the height) is the BLK is well known not to have a great level sensor, and there are some post around the forum about it not applying the level readings at all, so maybe you need to toggle levelled off in the registration and rely on the C10 to level up your data.

Cheers

Phill

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