Learning video on indirect registration

Post any education related material or training courses that are available to assist with getting users trained in laser scanning.
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jllerma
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Learning video on indirect registration

Post by jllerma » Fri Nov 28, 2014 2:37 pm

Let me encourage you to visit my learning video on indirect registration of laser scanning datasets. The users can find some theory on registration, practice using the software 3DVEM – Register and useful conclusions. Subtitles in English, Spanish and Valencià/Català.

https://media.upv.es/player/?id=9eaeba1 ... oplay=true

Best regards,

José Luis

rstuckey13
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Re: Learning video on indirect registration

Post by rstuckey13 » Fri Nov 28, 2014 11:23 pm

Thanks for that José,

What I find particularly good about this software is the thorough reporting of target errors, and the speed at which one can try different scenarios in terms of target choice. Being able to adjust the tilt compensator accuracy is also very handy, especially for my Faro, which seems to be far less accurate than stated on official spec sheet.
Now all I need for my Faro is some super-sized spherical targets.

Richard Stuckey.

Jason H
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Re: Learning video on indirect registration

Post by Jason H » Tue Dec 02, 2014 12:26 am

Richard,

SECO has some nice 230mm sphere targets in their scanner accessories section. You definitely need a steady base but they really help with range and are not too crazy expensive. The image is from a 68 meter scan and although it didn't come from a FARO it does show that you can really get some range from these spheres and a fair amount of point density which really helps with software automatically finding the targets.
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rstuckey13
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Re: Learning video on indirect registration

Post by rstuckey13 » Tue Dec 02, 2014 4:10 am

Thanks for that Jason, I'm seriously considering them, but at Christmas time, with all those Christmas baubles on sale it's pretty tempting to go the ultra-cheap way.
Correct me if you think I'm wrong, but it seams to me the accuracy achievable, especially at large distances, is far greater with spheres than with checkerboards. After all, you could have a checkerboard 10m high allowing the software to recognize the centre of target, but ultimately the accuracy of that centre is dictated by the spacing of scan points at the target, say for example 20mm apart, yielding an accuracy no better than 20mm. Whilst with a sphere say 10m in diameter, so long as the sphere is reasonably a true sphere, the software could pick the centre within a few mm.

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tadol
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Re: Learning video on indirect registration

Post by tadol » Tue Dec 02, 2014 7:51 pm

As an aside, I have some pretty nice 250mm target spheres as well - and I now have both magnetic mount and ⅝" threaded mount on them -

Just saying' -
http://www.KoppaTargets.com
Inexpensive Laser Scanning Targets & Accessories
for Architecture, Engineering, & Forensics
Now Available thru the FARO product catalog

Jason H
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Re: Learning video on indirect registration

Post by Jason H » Wed Dec 03, 2014 2:51 am

Richard,
I prefer the spheres at the long range mainly because while large and a bit difficult to carry around I don't need as many because I can pick them up from at a longer distance, I can see them from all sides and also as you say because you have less point spacing at the longer range, I feel better about extracting a shape rather than wondering if I really got the flat target true center. Where I see most people having trouble and getting frustrated with registration is when they have very few spheres like a three or five pack and then try to push the limits and get a bit farther than they should. It really should be as easy as clicking one button to find all your targets, put your project together and evaluate. That is why I am a fan of spheres big enough to pick up at range or else loading up with a lot of smaller spheres. Now on the topic of Christmas tree ornaments I do know of people who are blissfully happy using such objects as targets but I also know of people that would never use them as they would always have doubt. Mainly you are going to worry about laser absorption, roundness and in the case of setting them over control actually worrying about centering. I know SECO has obsessed over these things as I'm sure most proper target manufacturers have. Now if you are going to do a best fit based on the cloud after your registration it is probably a moot point. Often times I will mix the big spheres as tie points so to speak with more small spheres. Even if I am just doing a targetless cloud based registration I will throw in a few of the big spheres just for a sanity check since you really have no way of verifying other than overlap and confidence values. Now there are of course many more variables that could be considered such as the scanners performance at different distances etc... but I've rambled on long enough.
P.S. I did make a 24 inch checker target once but it was a bit unruly :)

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Re: Learning video on indirect registration

Post by jllerma » Thu Dec 04, 2014 11:08 am

Dear colleagues,

There is no doubt about the outperformance of spheres over other planar targets such as paddle and paper targets. The idea of different sizes is great!! Let me recommend you the following paper:

Burcin Becerik-Gerber, Farrokh Jazizadeh, Geoffrey Kavulya, Gulben Calis. Assessment of target types and layouts in 3D laser scanning for registration accuracy. Automation in Construction 20 (2011) 649–658.

Best regards,

José Luis

jllerma
I have made 10-20 posts
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Location: Valencia (Spain)
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Re: Learning video on indirect registration

Post by jllerma » Tue Dec 09, 2014 12:43 pm

Dear colleagues,

Besides the size of the target, keep in mind the geometry of your network. It is not a question of measuring many 3D points/targets. Avoid points/targets on flat areas and linear patterns!! Let me suggest that you do not always need large targets. At present, with fast and high resolution laser scanners, most of the times (if not all) you can find quickly points on the corners of high structures/buildings or just central parts of non-accessible features. The report will help you to understand the quality of your survey with 3D point across the area.

Best regards,

José Luis

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