Target Placement and Registration (BLK360)

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pilatquinton
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Target Placement and Registration (BLK360)

Post by pilatquinton » Wed Feb 13, 2019 9:56 pm

The company that I work for requires that some of our scans be within 1/8" due to the architectural nature of our scans. After fabricating our own 2D targets, we used them while scanning our latest job, and received mixed results. When the targets were recognized as being shared between two scans by Register 360 (I also occasionally had to manually point them out), the registration worked beautifully. However, many of the targets that should have been picked up by Register 360 simply wouldn't. There were targets that were lined up 180 degrees, about 15 feet away with great contrast, and Register 360 refused to pick them up. At the same time, targets that were 100 feet away on a crazy angle were being picked up immediately. Since these targets wouldn't pick up, I didn't have the minimum of 3 targets in common, and was unable to register strictly by targets. This forced me to register with autocloud, which of course wasn't as accurate. In essence, I have 3 questions:

1.) Would all of these problems be solved by the use of 3D targets?

2.) Since I am scanning buildings, do the targets need to be located on the building at all? Or can I have them in more convenient locations off to the sides and behind the scanner?

3.)Why are these targets not picking up? They have textbook placement and angle, but simply won't pick up.

I have attached a picture as an example of what I am having issues with.

Thank you for your time.
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Tookie
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Re: Target Placement and Registration (BLK360)

Post by Tookie » Wed Feb 13, 2019 11:11 pm

What do they look like in intensity only view? Some printed targets don't have good contrast between the black and white area in intensity which might be the problem.

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Re: Target Placement and Registration (BLK360)

Post by jamesworrell » Thu Feb 14, 2019 12:07 am

Tookie wrote:
Wed Feb 13, 2019 11:11 pm
What do they look like in intensity only view? Some printed targets don't have good contrast between the black and white area in intensity which might be the problem.
Also not the first time a target looks fine in colour, but in intensity someone has walked in front of it.

In this case, did the bobcat move? ;-p

Targets on objects than can move present a different problem. Not the first time our guys have put a target on a window and someone has opened the window. Roller doors is another past favourite. Some of our guys aren't real bright (aka Ernest). ;-p

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Re: Target Placement and Registration (BLK360)

Post by geomontgomery » Thu Feb 14, 2019 12:37 am

If you were to turn your images off, what does the point cloud look like in the region of your target?

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Re: Target Placement and Registration (BLK360)

Post by gsisman » Thu Feb 14, 2019 2:15 pm

pilatquinton wrote:
Wed Feb 13, 2019 9:56 pm
The company that I work for requires that some of our scans be within 1/8" due to the architectural nature of our scans. After fabricating our own 2D targets, we used them while scanning our latest job, and received mixed results. When the targets were recognized as being shared between two scans by Register 360 (I also occasionally had to manually point them out), the registration worked beautifully. However, many of the targets that should have been picked up by Register 360 simply wouldn't. There were targets that were lined up 180 degrees, about 15 feet away with great contrast, and Register 360 refused to pick them up. At the same time, targets that were 100 feet away on a crazy angle were being picked up immediately. Since these targets wouldn't pick up, I didn't have the minimum of 3 targets in common, and was unable to register strictly by targets. This forced me to register with autocloud, which of course wasn't as accurate. In essence, I have 3 questions:

1.) Would all of these problems be solved by the use of 3D targets?

2.) Since I am scanning buildings, do the targets need to be located on the building at all? Or can I have them in more convenient locations off to the sides and behind the scanner?

3.)Why are these targets not picking up? They have textbook placement and angle, but simply won't pick up.

I have attached a picture as an example of what I am having issues with.

Thank you for your time.
We have had the same issue at times with our BLK. The picture target and the intensity target response was good. We have gotten away from targeting manually using pictures (our picture is actually slightly out of alignment with the actual scan data -intensity and we need to send it for calibration.
The BLK'S work best with the HDS (Grey tone targets) -that is straight from Leica support. Also I think the angle of reflectivity has some bearing (although in your case and in ours that is not usually an issue when it misses one). It also seems to very easily auto pick it correctly when you choose B&W target in Register 360 using the Intensity to identify the target. This does add significant time, however ,you still need to go into each scanworld in register 360 and LABEL the targets if you want to use "Target Only" Registration or "Target-First" C2C Registration.
It seems to be a software glitch ,as sometimes it picks out non-targets that are much more poorly defined (when looking closely at the B/W cross pattern).
I think it may have something to do with how much the alternating intensity of the targets stands out against the background intensity behind them, especially with smaller targets. (You need about 10 scan lines on a target to get a very accurate target pointing coordinate) I've thought about constructing a kind of Target Collar -of a specific color that would provide a ring of a specific density completely surrounding the intended target (of course this would block out more behind the target but a bit more isolation (say 2-3") may be enough.

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Re: Target Placement and Registration (BLK360)

Post by Slewis33 » Thu Feb 14, 2019 3:01 pm

The company that I work for requires that some of our scans be within 1/8" due to the architectural nature of our scans.
I would rethink the use of a BLK if you have to hit 1/8". Targets or not the BLK360 was not designed to be a survey grade .01' tolerance laser scanner.

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Re: Target Placement and Registration (BLK360)

Post by pilatquinton » Mon Feb 18, 2019 6:05 pm

Tookie wrote:
Wed Feb 13, 2019 11:11 pm
What do they look like in intensity only view? Some printed targets don't have good contrast between the black and white area in intensity which might be the problem.
It surprisingly doesn't look too bad, possibly even better than with the photo!
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pilatquinton
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Re: Target Placement and Registration (BLK360)

Post by pilatquinton » Mon Feb 18, 2019 6:16 pm

gsisman wrote:
Thu Feb 14, 2019 2:15 pm


We have had the same issue at times with our BLK. The picture target and the intensity target response was good. We have gotten away from targeting manually using pictures (our picture is actually slightly out of alignment with the actual scan data -intensity and we need to send it for calibration.
The BLK'S work best with the HDS (Grey tone targets) -that is straight from Leica support. Also I think the angle of reflectivity has some bearing (although in your case and in ours that is not usually an issue when it misses one). It also seems to very easily auto pick it correctly when you choose B&W target in Register 360 using the Intensity to identify the target. This does add significant time, however ,you still need to go into each scanworld in register 360 and LABEL the targets if you want to use "Target Only" Registration or "Target-First" C2C Registration.
It seems to be a software glitch ,as sometimes it picks out non-targets that are much more poorly defined (when looking closely at the B/W cross pattern).
I think it may have something to do with how much the alternating intensity of the targets stands out against the background intensity behind them, especially with smaller targets. (You need about 10 scan lines on a target to get a very accurate target pointing coordinate) I've thought about constructing a kind of Target Collar -of a specific color that would provide a ring of a specific density completely surrounding the intended target (of course this would block out more behind the target but a bit more isolation (say 2-3") may be enough.
I found that 360 would find targets in really strange places (a window mullion for example), but would refuse to find one 5 feet in front of it. I think your target collar idea would work nicely, I was thinking of something along the same line as well.

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Re: Target Placement and Registration (BLK360)

Post by Tookie » Mon Feb 18, 2019 7:27 pm

pilatquinton wrote:
Mon Feb 18, 2019 6:05 pm
It surprisingly doesn't look too bad, possibly even better than with the photo!
Looks like it should work.. is the aliasing from the screenshot or the scan (I see a white bit on the left and a black bit on the right where it shouldn't be) ?
I guess bigger targets are the answer. Or a bigger scanner ;-).

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Re: Target Placement and Registration (BLK360)

Post by pilatquinton » Mon Feb 18, 2019 9:29 pm

Tookie wrote:
Mon Feb 18, 2019 7:27 pm


Looks like it should work.. is the aliasing from the screenshot or the scan (I see a white bit on the left and a black bit on the right where it shouldn't be) ?
I guess bigger targets are the answer. Or a bigger scanner ;-).
The aliasing is from the scan. Maybe we should be using 12in. targets for what we're doing, since our scanning subjects are so large in scale. I'll have to run that by the boss, not the new scanner part of that though, I don't think he would like that :lol:

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