Underground laserscanning projects

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MagicBrou
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Underground laserscanning projects

Post by MagicBrou » Fri Dec 14, 2018 4:18 pm

Hey guys,

Currently i am working on a Underground floor of a huge building. It is not able to measure total Station points inside the floor from the outside to georeference the floor. The only possibility to do that would be doing a Cloud to cloud connection with stairways from the upper floors. With my experiences, it is not very accurate because everything relies in the stairways Connection and especially the Level or z-values are pretty bad...

My idea would be, measuring a polygonal Chain through the entire Floor and determine 4-6 paper Targets in the Corners of this Floor to georeference the whole Floor. You can also use a optical leveler
in advance on the paper targets to enhance height accuracy of those points.

I find this method very time-consuming...but also pretty accurate.

How would you solve this problem ?

Wdigman - Europe
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Re: Underground laserscanning projects

Post by Wdigman - Europe » Fri Dec 14, 2018 4:41 pm

Julian,

If there are multiple stairways I would connect the lower levels with targets to the upper floors through the stairways. To accumulate enough error to lose an accurate Z would have to be a long stairway. You said multiple so I assume there is more then one stairway.

Also in the lower level shoot some targets with a total station or run a level, to check z and possibly adjust if needed.

I have worked in confined spaces in Nuclear plants where the use of survey was not practical, we used level loops to double check if the resulting registration was out of level, it worked.

IM me if you still have questions. Currently in Latvia.

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steves01x
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Re: Underground laserscanning projects

Post by steves01x » Fri Dec 14, 2018 4:59 pm

If you have 2 or more stair cases either as mentioned above you could:

Put targets in the stair wells where you can easily get in to the building with the Total Station and pick them up then scan down in to the basement and back up the other stair cases picking up your well spread out targets,

Or just scan from one staircase along the upper floors to the other staircase, down it, through the basement and back up the next stair case closing the scan loop. Cyclone & P series scanner is brilliant for these things.

Or stick additional targets up and get someone to traverse the same route your scanning with a Total Station for a double check!

MagicBrou
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Re: Underground laserscanning projects

Post by MagicBrou » Fri Dec 14, 2018 6:39 pm

Thanks both of you for the answers,

It is a large building about 100x30m and the stairways are in the middle of the building on both Ends. Because of this, i am not sure about the loop because the error will get bigger throughout the huge length of the building
.. like i said i tried to register it through the stairways but the whole floor is tilted in the width.if i compare the windows with the interior and the exterior, you can see the error in the height about 5cm :-(... So how do i correct it properly? My thought was, that i Put paper Targets in the Corners and then measure those with an optical leveler. Then i would Change the z values of These Points in the Scan and re-register it. But i am not very Happy with that :-(. I use Faro Focus x130 and Trimble realworks...

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Re: Underground laserscanning projects

Post by steves01x » Fri Dec 14, 2018 7:58 pm

I have never used Trimble software so no help there but I think one problem will be as you used a Faro and you have no idea if it's level or not and over the distance of all the set ups it's slowly going off.

Do you have access to Cyclone to see if pumping in there then optimising the constraints improve anything?

MagicBrou
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Re: Underground laserscanning projects

Post by MagicBrou » Sat Dec 15, 2018 3:13 am

No i don't have it: (... Maybe ITS only possible the corrected by a polygonal chain

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Re: Underground laserscanning projects

Post by steves01x » Sat Dec 15, 2018 12:37 pm

Is it the completed registration of basement (scanned in a loop) that is tilted or random scans tilted / not registered correctly? Can you generate a registration report and the numbers should guide you to where the problem is?

Can you turn the scans to un-levelled and use one that you know is correct / level from an upper floor and set it to a home/main scan? Then assuming that one is correct/level, c2c with a scan at the start of your loop and at the end it should shift everything to the correct location?

I have seen massive drift even with spheres on the Faro when we used it to scan internals on a large project compared to identical building scanned externally and internally with P40, it was as good as perfect when checking the data.

If you are going to get a Total Station in get them to traverse in/out of the basement using 2 different staircases, pick up a good amount of paper targets on stairs/basement and spheres (go back and scan them at a high resolution), c2c those new scans in to the existing and you should be fine.

MagicBrou
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Re: Underground laserscanning projects

Post by MagicBrou » Sat Dec 15, 2018 12:49 pm

Alright i'll try this methods on monday and give you a quick report about the results... It is so embarrassing that WE bought a Laserscanner with a Bad compensator... I think i will Switch to Faro S series. Still a small device with enhanced compensation in comparison to the x series. Thanks very much

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Re: Underground laserscanning projects

Post by steves01x » Sat Dec 15, 2018 3:19 pm

Can you not return it or get it sorted at its annual service / calibration?

MagicBrou
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Re: Underground laserscanning projects

Post by MagicBrou » Sat Dec 15, 2018 4:35 pm

We will do that, but it will cost about 3000 to 6000 euro.
Pretty expensive! And with No doubt, the compensation of Faro Scanners is pretty bad

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