help:registration technique of 500 scans in RW

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blazaj
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help:registration technique of 500 scans in RW

Post by blazaj » Wed Apr 18, 2018 4:11 pm

Hi,

I'm new to Real Works and just got demo license to test registration on a job I did recently of a 4 storey building (app. 500 Faro Focus scans). I imported all FLS and now I'm a bit lost. Do I have to sample the imported data first? Do I create clusters like in Faro Scene and register from small blocks upwards? I have some scans with targets, some without, can Real Works combine scan based registration with targets?

I tried automatical plane based registration on exteriors (app. 50 scans around the building) and it worked smooth and the results were good. I tried interiors - a single floor of app. 100 scans and it did not. Is it too many scans to register together in one group? How do I refine registration?

Many thanks for your help!
Jiri

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Re: help:registration technique of 500 scans in RW

Post by apjokr » Thu Apr 19, 2018 8:12 am

Hi Jiri,

OFF
I believe it is a good manner and better approach to give a training beside the trial licence otherwise a potentional customer just get confused instead of getting to know the software.
ON
Without giving an online training here I can make you calm about the possibilities, you can handle it. Perhaps starting with these milestones you can contact your local supporter on the exact How to.

-After importing you always need to use the 'create sampled scans' command to derive from the raw data.
-For these numbers of stations yes, you need to use 'clusters' which is called 'groups' in TRW. (Edit menu>New group)
The stations included in the group will not move if you are working on an other group, hence you are able to register the different stories independently first, or however your approach is applied to the project.
-Then you can register the groups to each other, and yes you can use multiple features combined which registration method you need.
-Auto-planes is robust and reliable, will help you in several situations. In regards to the amount of scan and site-characteristics, it may take long time or can be not efficient but the reason of the long-lasting calculation can be if you have indoor measurements is:
Imagine 2 iteration during the registration. The first is to align approx the 100 scans to each other, finding the neighbours. Secondly it will be the 'Refinement' to align the scans in the most possible accuracy.
So you can imagine that the first step is much easier outdoors because I believe you have a station with at least 3-4 other neighbours having overlap, while indoor it can happen that all neighbours are almost in a different room/less overlap so the 100 station has 99 other possible neighbours, and so on so on.

This does not mean that the software is limited indoors - it needs a different approach already on the field, and in the office when you plan which method you are supposed/want to use.
Last edited by apjokr on Thu Apr 19, 2018 3:54 pm, edited 2 times in total.

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Re: help:registration technique of 500 scans in RW

Post by blazaj » Thu Apr 19, 2018 8:23 am

Hi Robert,
thank you for your help! I'll give it another go. I e-mailed the dealer for support but I'm too impatient to wait for response. I was surprised it placed all 100 scans, apart form one, approximatelly well relating to each other, but I was put off by the time it took and I couldn't refine the whole bunch. I'll give it more Scene like approach and see where I get.
Regards
Jiri

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Re: help:registration technique of 500 scans in RW

Post by apjokr » Thu Apr 19, 2018 9:50 am

If you run the Auto-planes and you see 1 station is misaligned, then put this scan outside the Group.
Then run the 'Refine registration using scan' (small icon) choosing the already well-registered Group as the reference, and the 1 mis-aligned will be the moving station. Even better to create a group with the properly aligned neighbour stations only to reduce processing time. As I told you, the stations in the group will not move but thanks to the first step now they have a properly aligned better coverage to make that 1 single station to move to its correct place.

To proceed this I recommend especially if you have the mis-alignment in elevation, find the command 'Force unleveled' as fls usually comes from an instrument having a non-high-end inclinometer and does not let you align properly during the registration process.

Looks difficult but just a mixing of 'clusters' and the other station under the List window.

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Re: help:registration technique of 500 scans in RW

Post by blazaj » Fri Apr 20, 2018 1:21 pm

Thanks again,
I imported much smaller project ~50 scans, idoors + outdoors and it registered well without any external help. I just wonder if there is a way to segment individual TZF files or sampled scans prior to registration to get rid of glass relections etc.?
Jiri
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Re: help:registration technique of 500 scans in RW

Post by apjokr » Fri Apr 20, 2018 1:56 pm

Nice :)

After performing the Registration, switch to the Production module by clicking on the up-left corner.

Here you can perform more editing/downsampling on the cloud, then create further deliverables , accordingly to the licence you have.

The List window contains the 'Project cloud' which insists of all the sampled stations what you have done in the previous step.
Use the Segmentation tool to fence the area of your interest.
Use the Sampling tool if needed - you will most probably understand which setting what will be result of the features what you find there.

The area what you have created will be stored under the List window and can be exported in multiple formats.

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Re: help:registration technique of 500 scans in RW

Post by blazaj » Mon Apr 23, 2018 10:30 pm

I tried a more complex registration. Roughly 200 scans of a railway station. No targets this time. I made groups of different parts - platforms, offices, waiting room, ticket office, street etc. and auto registered each group. Then I picked 12 groups containing the exteriors and rooms on the 1st floor - approx. 150 scans alltogether. I auto registered again and it took well over two hours. The result looked good on first sight, but as I investigated more I found misalignments in vertical sections. I'm trying to refine each group now to get better results. Is the time it took to register something I can expect? Is 150 scans too many to auto register without targets?

P.S. I like Realworks ambient shading -
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Re: help:registration technique of 500 scans in RW

Post by blazaj » Wed Apr 25, 2018 10:16 am

In the next step I used Auto Plane on the individual floors to register it together. In total 209 scans in several pre-registered groups. It took all day to compute! Results looked good, but for one troubled area I already had problems with when originally registering in Faro Scene. It is a long corridor conneceted to the main staircase on one side of the building, no loop closed. It had a small angular misalignment on the joint which pronounced all the way along the building. As a result I got a wedged outer wall, thinning several cm's at the end. I used slab targets to refine the registration in Scene and it got resolved.
Interesting enough I got the exact same misalignment after Real Works registration. I tried to shuffle some connecting scans around the groups, tried c2c on top of the Auto Plane registation, but it did not help. As I have no sphere or checkerboard targets in the area and can't use slabs as in Scene I don't know what to do next to resolve the issue. Any suggestions?

Thanks
Jiri

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Re: help:registration technique of 500 scans in RW

Post by apjokr » Wed Apr 25, 2018 10:47 am

According to my experience by measuring long corridors, even if you have a loop, you can easily fall into this situation you explained.

Regardless the method you will have bad orientation of the sphere-targets due to the narrow area. Same applies to the planes what you want to extract-you don't have them, only in 1 direction mainly.

I have a user who went back to measure the corridor in one loop. Does not matter. For these amount of scans and multiple floors I always teach the users that it's better to have survey control at each floor at the staircases because you will never escape the building and here it is not an issue with Trimble RealWorks.

Robert

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Re: help:registration technique of 500 scans in RW

Post by blazaj » Wed Apr 25, 2018 11:06 am

Thanks Robert,

I'm not saying it is an issue with the software, I'm trying to find out a solution on the registration part. I was able to do so in Faro Scene. I created pairs of "slab" targets to walls one from a scan in the corridor, the other slab in a scan containing the opposite side of the wall and entered known wall thickness. Then I used this slab pairs in target registration, which fixed the problem. Is a similar method in RW?

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