Registering scans using surveyed targets

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adriantaylor09
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Registering scans using surveyed targets

Post by adriantaylor09 »

Hi guys,

I'm looking for some advice before embarking on a rather large scan job which involves several multi level buildings.

For this job, rather than try and link each floor together by scanning up and down stair-ways, I figured it'd be much easier to survey the position of several sphere locations on each floor. That way each floor can be registered as its own cluster in Scene and each cluster can be registered globally using the surveyed sphere locations.

Luckily, in this case, the buildings are open steel structure (i.e. no walls), which means that I can place my sphere targets in a position that can be seen from both inside the building and from the ground level. I'm hoping that this simplifies things from a surveying point of view, in that the surveyor can operate from the ground level only.

So my questions....
  • has anybody had experience with an approach like this before? if so are there any traps to watch out for?
    Realistically, how many spheres should I be aiming to survey on each level? I'm guessing that 3 is the minimum but more is better?
dbianculli
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Re: Registering scans using surveyed targets

Post by dbianculli »

I'm guessing that 3 is the minimum but more is better?[/list][/quote]


I suggest a minimum of 5 spheres for each station. matematically speaking 3 is the minimum number to solve the network but in the real world is much better to have more than the minimum. What instrument are you using? Diameter of spheres?
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Re: Registering scans using surveyed targets

Post by adriantaylor09 »

Yeah I figured 3 would be bare minimum. I guess it's always a balance between cost and accuracy
dbianculli wrote:What instrument are you using? Diameter of spheres?
Laser scanning will be done with a Faro Focus 120, diameter of spheres will be the standard Faro spheres which I believe are 140mm in diameter.
Surveying will be done by another contractor, so he will use his own weapon of choice I guess

We actually have some custom made 'discs' that we weld/bolt/glue permanently to structures that we scan. These discs then serve as magnetic mounting points for our spheres. This way, you can re-visit a scan location, use these mounting points and be pretty confident that your spheres are in the same location each time
disc.jpg
And we've got a prism target for a surveyor that will mount to these discs such that the center point of the target is in the same location as the center of a sphere. Until now we've just never really used this approach on a big job before, which is why I'm interested in other peoples experiences
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Re: Registering scans using surveyed targets

Post by Oxbow »

hi,

you should have more as 3 targets for each scan, otherwise aligment (adjustment) is not possible.

we have also precise adapter for spheres as complete solution in our webshop. bigger spheres as well.

best regards.. ..eric
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Re: Registering scans using surveyed targets

Post by MarkoMatilainen »

Hello Adrian,

You are right, three spheres is minimum, however, ideally you should have a sphere in every quadrant, so in reality you need more than three and five is a good start. It all depends on the environment you plan to scan.

ATS has developed a Quality Manager App for FARO Scene, you’ll find it in FARO App-center: http://www.faro.com/faro-3d-app-center/ ... ug-in-apps

This app is a very useful tool to verify and report the quality of the registration in FARO Scene, you’ll get a very detailed report on how good the sphere distribution is. You can also use the app during the registration process (in Scene) as it allows you to see the quality of the references.

Furthermore, ATS SRS (Scan Reference System) is a fully integrated system for scanning and surveying (total station), with a signal height of 196mm. ATS SRS is based on precision washers and targets, in this case spheres (all spheres and adapters has a magnet connection). We can sell you these washers.

With a prism you can survey the position of the mounted precision washer, which you also use for the sphere and build your local, or global, coordinate system. This is how most of our customers use the ATS SRS.

ATS is the supplier of the spheres you have. FARO Standard Medium Sphere 140mm (139mm), range up to 20m and the FARO Standard Large sphere 200mm (198,8mm) has a range up to 40m.


If I can be of any assistance, you are always welcome to contact me!

Marko Matilainen
ATS AB
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