Homemade Targets?

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pilatquinton
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Homemade Targets?

Post by pilatquinton »

I have now been scanning with the BLK360 for about 8 months now, and have learned a lot along the way. Registering scans with targets simplifies the workflow, and makes my scans accurate as ever....if Register 360 even picks them up. We have a series of homemade 2D targets (paper adhered to 6"x6" steel squares), and while they work great in some cases, they are practically useless in others. Register 360 simply doesn't want to pick up these targets, or if it does, it doesn't pick the correct center.

Is this just a case of our homemade ones not being "good enough"? The prices that these manufacturers charge for 2D targets is outrageous, and I have yet to find any evidence that the materials/process they use to make them will make them anymore successful than the ones we fabricated in our shop.

We have also been attempting to fabricate our own spherical targets for some time now, and have had zero luck in getting Register 360 to recognize them.

Have you guys made any homemade targets? What materials did you use, and how successful were they? Please post pictures as well, I'm really curious to see how different everybody's look!

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Re: Homemade Targets?

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Re: Homemade Targets?

Post by geomontgomery »

pilatquinton wrote:
Mon May 06, 2019 5:49 pm
I have now been scanning with the BLK360 for about 8 months now, and have learned a lot along the way. Registering scans with targets simplifies the workflow, and makes my scans accurate as ever....if Register 360 even picks them up. We have a series of homemade 2D targets (paper adhered to 6"x6" steel squares), and while they work great in some cases, they are practically useless in others. Register 360 simply doesn't want to pick up these targets, or if it does, it doesn't pick the correct center.

Is this just a case of our homemade ones not being "good enough"? The prices that these manufacturers charge for 2D targets is outrageous, and I have yet to find any evidence that the materials/process they use to make them will make them anymore successful than the ones we fabricated in our shop.

We have also been attempting to fabricate our own spherical targets for some time now, and have had zero luck in getting Register 360 to recognize them.

Have you guys made any homemade targets? What materials did you use, and how successful were they? Please post pictures as well, I'm really curious to see how different everybody's look!
I was at a customer's site recently who drew their own 4" B&W targets in CAD and printed them as a way of getting around having to purchase targets, and they were seeing success. Where the paper targets were limited was with acquiring points in non-perpendicular planes to the scanner position, it seemed that the printed targets were too shiny on standard office paper and didn't reflect light back to the scanner as well as other targets.

Where you could get around this is probably your choice of paper and method for printing the targets. I just wanted to chime in and say others are trying the same thing and can get targets detected by making their own. I really don't think there's anything special about the geometry of the target itself, but rather it's materials of construction and your workflow when using targets.

How are you mounting the B&W targets in the field? I've seen more success with the targets angled at a 45 so the B&W areas make an X pattern vs positioning them straight up and down. There was a thread last year about how this type of positioning helps the software detect the target center better, since the laser travels up and down when it acquires data so you capture more transition points between B&W areas. Seems to make logical sense but someone else might be able to chime in whether this is true or not.
Last edited by geomontgomery on Mon May 06, 2019 7:16 pm, edited 1 time in total.

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Re: Homemade Targets?

Post by mstachoni »

I've been using homemade targets on a VERY large construction project ($1.4B, 1.5+M SF) quite successfully. We are constantly scanning and have a need for literally hundreds of targets permanently mounted around the job site. I initially started with 6" targets printed on simple Avery address label paper, stuck to 8"x8"x3/4" painted MDO plywood with a quick coat of polyurethane. MDO is B-grade plywood with a very smooth MDF face on one side, perfect for mounting targets. We use MDO for concrete formwork, so I had my superintendent pull a few sheets aside for me. I cut them up in my home shop and drilled a hole in each corner to tie them to the fence using 16ga wire, about 40' apart. They absolutely do not move. I've also made up a set of targets on 1/8" hardboard which, with a coat of paint, work well too.

I also re-created the target graphic from scratch in Adobe Illustrator instead of using the Word file that came with our Leica P40 scanner. The original target color was gray, so I made mine strictly black and white. I tested it under different conditions and it works great.

Unfortunately these cheapo labels only lasted about a month in the New Jersey winter weather before the paper started peeling and disintegrating. I found www.stickermule.com and ordered 200 square waterproof stickers (about $300). I made up another batch of MDO squares with the stickers and installed them about a month ago. The adhesive is excellent and they still look brand new, even without any polyurethane protective coat. Each one gets a unique label and is surveyed with a total station so we can easily ID them in Reg360 and apply control. We typically don't bother capturing targets in the scanner in the field, because it takes too long per setup. Finding them in Reg360 is easy enough.

I have about 50 extras that I can mount to rough work using construction adhesive. A hot glue gun also gets the job done and is better for mounting temporary targets for final interior finishes that only need to stay up a few days and/or won't damage the substrate coming off. I have the Ryobi battery-powered glue gun that is really nice for field use.

I also bought 100 8"x8" printed target magnets (about 1/32" thick, about $4/magnet) which we mount to the bare structural steel. They are similar to magnetic signs you see on cars. They are exceptionally strong - they haven't budged a bit in three months. We have less than half the steel up so I'm getting ready to buy another 200.

Because the project is so large physically, we cannot easily acquire targets on the fence while setup in the building all the time, so the mag targets on the steel columns and beams are perfect. We also make high-resolution detail scans of any targets more than 50 feet away (one of the reasons we love our P40). That saves a lot of fiddling in Reg360 in finding targets and being able to precisely find the center.

Assuming you are doing mostly interiors-only, short-range work with the BLK, I would look at getting a set of electrostatic targets. Not that expensive, they are reusable, and they stick to interior protected surfaces quite well.

I wanted to try DIY spheres, but after doing the research found that the build tolerances required were very high. While more flexible than flat targets, they are bulky and would likely get destroyed on a busy job site like this. We also invested in three Seco steel tilt'n'turn targets that we mount on tripods setup over control points or when scanning a large blank area in the middle of nowhere.
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Re: Homemade Targets?

Post by pilatquinton »

geomontgomery wrote:
Mon May 06, 2019 6:54 pm

How are you mounting the B&W targets in the field? I've seen more success with the targets angled at a 45 so the B&W areas make an X pattern vs positioning them straight up and down.
When I put targets up, I try to cage myself in between 2 larger ones, and spread the smaller ones in between. I use the large ones as reference points, and these stay at 90 degree angles relative to the scanner. They end up being in every scan, if possible. I have thought a lot about what material is located behind the targets, and I think the steel we are using is just too reflective. I'm thinking maybe a coat of matte paint behind the paper might reduce the reflectivity and give us better reads on the targets.

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Re: Homemade Targets?

Post by pilatquinton »

mstachoni wrote:
Mon May 06, 2019 7:12 pm

I also bought 100 8"x8" printed target magnets (about 1/32" thick, about $4/magnet) which we mount to the bare structural steel. They are similar to magnetic signs you see on cars. They are exceptionally strong - they haven't budged a bit in three months. We have less than half the steel up so I'm getting ready to buy another 200.

..............

Assuming you are doing mostly interiors-only, short-range work with the BLK, I would look at getting a set of electrostatic targets. Not that expensive, they are reusable, and they stick to interior protected surfaces quite well.

I wish we could just leave the targets on the site like you do! I can't tell you how much time I waste just moving targets back and forth. Are these magnet targets printed already? If so, where did you get them?

I'm currently using the BLK on building exteriors. It does pretty well, but our accuracy really falls on how well I register everything, which is why I try to use targets when I can to improve my accuracy.

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Re: Homemade Targets?

Post by mstachoni »

I wish we could just leave the targets on the site like you do! I can't tell you how much time I waste just moving targets back and forth. Are these magnet targets printed already? If so, where did you get them?

I'm currently using the BLK on building exteriors. It does pretty well, but our accuracy really falls on how well I register everything, which is why I try to use targets when I can to improve my accuracy.
Actually leaving the targets up was the only way to make this job sane. You get used to using the same target IDs between registration projects which makes the office work faster.

The magnetic targets were printed and delivered from www.stickermule.com as were the vinyl waterproof stickers. They were inexpensive and only required me to upload an .ai adobe illustrator file of the target graphic. Ordered and had them within the same week. Very satisfied customer. Can’t believe how well they hold in rain, sun, and snow. The vinyl targets have a really good adhesive too. They look shiny in the pictures but they work great with the scanner.

In my opinion The BLK really isn’t meant for exterior work. I’ve done it and scanned stuff that by all rights should have been done with a better scanner. The range is way too low and the accuracy is pretty bad at typical exterior scan ranges. Plus you have almost zero control over the quality and downloading the data by wireless is really awful.
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Re: Homemade Targets?

Post by Jason Warren »

For some projects its worthwhile having some targets printed on thin metal plate.
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The brass connectors on Reuben Heaton gauge boards are a useful accessory for using homemade targets with bank sticks and range pole supports.
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Lastly its always worth having some targets printed double-sided ;)
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Re: Homemade Targets?

Post by tadol »

Its kinda amazing how hard it can be to make something as simple as a sphere. And I definitely understand the appeal pf trying to figure out an accurate and inexpensive way to do it. But . . . .

I’ve worked pretty hard for some years to build spherical targets that are lightweight, accurate, come standard with multiple mounting options, and are relatively inexpensive. Since you’re a member of the LSF, please email me and I can give you a small discount automatically, and if you need lots of targets, I can help with that too. You may find that your efforts are much better spent promoting your skills and getting more work, rather than painting balls -

I’ll be at SPAR in a couple weeks, with some exciting new product announcements that may be exactly what you want - hopefully I’ll be able to help you out - but feel free to get in touch if you need any help or advice trying to roll your own -

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Re: Homemade Targets?

Post by ScottErnst »

I've had good luck with printing my own targets. The BLK is supposed to prefer grey & white over B&W but I haven't noticed a difference.

I also bought some 6" Christmas ornaments to use as spheres and painted them matt white, figuring that it was an inexpensive way to give it a try. I could not get Register 360 to pick those up except from about 10' away. I was curious about that and ended up borrowing a set of Koppa spheres and doing a comparison. I put one of each at 10, 20, 30 & 40'. Register 360 couldn't recognize either of them except at 10'! I mentioned it to a Leica employee and he said that the software needed work. (sigh)

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