Paper Targets vs. Traversing; Need feedback

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scannerdude
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Paper Targets vs. Traversing; Need feedback

Post by scannerdude » Tue Jul 02, 2013 3:55 pm

Hello All,

I scan mostly buildings with a Leica P20. I use the Cyclone software to do my registration. I have found it much easier on the registration side to bring in a traversed job rather than a free scan job with paper targets. The only issue I am having with a traversing job is setting control points in a occupied building. Unfortunately you cannot scribe X's on a finished concrete floor, so does anyone here have any suggestions on that? I find it much easier to traverse rather than hanging paper targets in the field as well. Just looking for input on field practices for scanning. I get the job done, just looking for tricks of the trade. Hope to hear something back.

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Re: Paper Targets vs. Traversing; Need feedback

Post by andrew.grigg » Tue Jul 02, 2013 4:30 pm

I use Tippex (other liquid paper brands are available :) ), which you can scratch off afterwards. Not ideal I know. I think it's possible to combine both traverse and C2C/targets, but I haven't tried this myself, other than creating vertices manually when joining 2 projects.

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Re: Paper Targets vs. Traversing; Need feedback

Post by LEIGH DICKSON » Tue Jul 02, 2013 9:19 pm

Could you not use this: (They stick to anything - although they may take the paint off of a poor paint job on a wall)
Would your scanner pick this up - can you do a resection?

http://www.phoenixse.com/reflective-retro-targets.html

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Re: Paper Targets vs. Traversing; Need feedback

Post by TimBeach » Tue Jul 02, 2013 10:10 pm

The P20 wouldnt pick them up to resect on - but you could use them to stick to the conc floor to set up the stations of your traverse over - plus you could remove them at the end of the job.

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Matt Young
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Re: Paper Targets vs. Traversing; Need feedback

Post by Matt Young » Wed Jul 03, 2013 10:00 am

As Tim says, scanners won't like reflective targets, you just get a kind of small very noisy area on them in the scan.
If you don't see that there is nothing, then you are kidding yourself.

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Re: Paper Targets vs. Traversing; Need feedback

Post by Andrew » Wed Jul 03, 2013 12:21 pm

To mark station locations I sometimes use small circular vinyl self adhesive stickers. These are printed with alternating black/white quadrants - the intersecting edges mark the control point.
Vinyl Marker.png
They do last for quite a while, unless the cleaner hasn't been told not to spend all morning scraping off your previous day's traversing!

There are online companies that will print these for you. I can't remember who we used - search for 'circular vinyl stickers'.
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Re: Paper Targets vs. Traversing; Need feedback

Post by Toulinash » Thu Jul 04, 2013 11:34 am

I have a question when it comes to traversing.
Do you use the special leica targets on the tripod? (center of marker = center of scanner)
And what happens if you get inside and it appears that in one of the stations something has gone wrong, does cloud to cloud registration still work in cyclone when you don't have a lot of bleed? ( is that the right word for overlapping pointclouds?)

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Re: Paper Targets vs. Traversing; Need feedback

Post by stevenramsey » Thu Jul 04, 2013 2:56 pm

Why don't you not bother marking the ground, Using the two tripods as fixed centers and swap target for scanner. instrument height is zero. You just need to be careful like you would do with a Total station.
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Re: Paper Targets vs. Traversing; Need feedback

Post by Andrew » Thu Jul 04, 2013 3:06 pm

If the survey will take more than a day I find having control on the ground is a good idea when you come to carry on your traverse. Also, if a tripod was to get knocked during a traverse your life would be a whole lot easier if you had a mark to centre over again.

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Re: Paper Targets vs. Traversing; Need feedback

Post by scannerdude » Sat Jul 06, 2013 5:25 pm

Thanks all for the informative input.

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