Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

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Scott.Warren
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Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by Scott.Warren »

Hey Folks,

Curious to hear what experiences the group has with scanning the underside of bridges for details where access is only feasible from the bridge deck. I'm looking online through rent-able Camera Jigs, where I assume a boom truck would be unable to be still long enough for a scan, especially if there is an operator in the bucket too. Our goal is detail on gusset plates, providing bolt spacing/patterns for structural analysis. We'd likely use a lighter scanner (Faro/RTC). We are not trying to correctly georeference the scans, only see if there is a method of free-scanning that would be an improvement over climbers/ropes.

Any ideas worth trying, or worth avoiding?

All the best,
Scott
Last edited by Scott.Warren on Thu Jan 16, 2020 6:01 pm, edited 1 time in total.

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by WWilford »

I have used a 15 meter carbon fiber mast to scan from. Guy wires are necessary past 20' in elevation. Pneumatic 60' mast is stable at full height with no wind, 30' with moderate wind, can use guy wires to stabilize.I have researched the camera booms and most do not lock very well to keep them stable. Boom lifts could be stabilized with guy wires as long as they are used in a way not to compromise weigh capacity ratings.

Possibly use laser scanning to establish scale and combine it with high resolution photogrammetry from a drone?

If you have a specific project in mind please drop a line or give me a call. There is always a solution.

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by Scott.Warren »

We are trying to get information under the bridge, so going up isn't the issue, so much as going down and around.

Our concern with photogrammetry Drones is to use the Metric camera we have, we'd need to setup control targets near the object, which would need climbers, which negates the use of the drone in the first place. UAV work isn't my forte, but this is work where we need accuracy QAQC beyond relying entirely on the software.

I don't think i've seen a UAV Lidar dataset which seems up to snuff to measure to finer details on these plates, to what we are chasing in accuracy.

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by WWilford »

I think we can get the resolution needed. Scale could be established after meshing with a laser scanner. I am not sure how to get QA/QC from other than software without getting hands on.
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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by jcoco3 »

Hi Scott,

For some strange reason I have spent most of the last two years tackling these types of big bridge projects. Unfortunately most of them are two sensitive to post pictures and talk about directly (big bridges have big $$$ problems).

Every bridge is a different story and it is kind-of difficult to make recommendations not knowing more about the environment. I can only offer some of what we have learned. Much like Warren has suggested, start from the ground if you can. We have been able to obtain really nice looking data from longer distances at ground level, and in 6' deep calm water with large tripods on hard clay bottom. Lots of survey control and additional overlapping scans to confirm results (which takes forever), but is so much easier than hanging a contraption off the side of the bridge. Having said that we have done too many hanging and cantilever scans from bridges with good and bad conditions. Good being no wind and no vehicle traffic. We threw together a terrible looking "battering ram" bracket thing on wheels made from large diameter emt conduit and angles the weekend before a big project on a short schedule. It stuck off the side of the bridge ~15'. Initially we used guy wires to attempt to stabilize the scanner. The results were usable, but we improved things by adding some long legs that projected back to the side of the bridge deck. We used boards and wedges to pull/pry the contraptions back to put some force into the legs. We basically created a big sideways tripod, which was a marvellous improvement in stability and deployment. We have also done many hanging vertical scans...way too many for stockpiles, and the number of precarious bridge scans in that orientation is also adding up to unpleasant numbers :roll: If you can I would suggest an upside down tripod approach, but of course the practicality of the constructing, deploying, and successful use depends heavily on the bridge geometry near the barrier rail, the length of the bracket required (better to do many scans with a shorter more stable bracket, than few with a long wiggly one), and probably a bunch of other factors that I can't remember right now. As far as the bucket truck goes...not for me, too scary, and too unstable. I did a bunch of 1/2 res scans (in the freezing wind and rain) under a big bridge one time on some of the best (most well constructed and rigid) scaffold I have ever been on. Due to high wind gust, even then the scaffold movement was too much for my liking, so I mounted the scanner upside down using a big beam clamp to a massive diagonal steel member, which was experiencing almost no vibration by comparison. Point being, if you want to use a bucket truck or reach-all to get under the bridge from the deck level, then consider bringing some sort of clamping bracket that you can mount the scanner to the bridge with to avoid the bucket truck movement. Needless to say vehicular traffic can create a mess in terms of scan data quality, so if the bridge will be shut down you might be in luck. We have unfortunately scanned in almost every conceivable worst case scenario for bridges, so fire away if you have more questions.

I really wish I could share some pictures. Many of the things we have tried and challenges we have face are too funny not to share. I can paint at least one picture for you. We had a gentleman from another company we affectionately named "Spider-Man" who used climbing gear and ropes to dangle underneath a bridge to place some of our cheap home-made 8" spheres with 70lb force magnets upside down hanging from the bottom chords. We chose to use the spheres in this case for ease repeatability in a flurry of scans over a few days of work in the same area. Watching him climb down in the freezing wind made my pulse race, I have a funny video I also cannot share. That guy was my hero for the week! Those spheres are still where he put them after many months, because there was no way I was going to ask him to do that twice :lol:

If you do decide to go with a tall mast, then Warren has the tool to dominate the sky for you.

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by Scott.Warren »

jcoco3 wrote:
Thu Jan 16, 2020 7:32 pm
Point being, if you want to use a bucket truck or reach-all to get under the bridge from the deck level, then consider bringing some sort of clamping bracket that you can mount the scanner to the bridge with to avoid the bucket truck movement. Needless to say vehicular traffic can create a mess in terms of scan data quality, so if the bridge will be shut down you might be in luck. We have unfortunately scanned in almost every conceivable worst case scenario for bridges, so fire away if you have more questions.
This is more what I'm getting at,looking at interesting ways to mount and place a scanner. I guess the question i'm posing is more of experience using something like this:



Our bridge is over deep water, with 2 very tall piers in the watercourse, where our plates are. Even from shore, there are cliffs/vegetation further limiting where we can occupy. If we wanted to sit in the watercourse for a better angle, we'd have to bring a barge with spuds to have chance at a stable platform, which seems excessive, his is why we are looking at the boom option. We are not trying to capture the entire bridge, only a few plates and connections in hard to reach places on the center piers. Having something that we can use to swing the scanner into position, and use the RTC's tablet to check coverage should be sufficient.

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by jcoco3 »

Strikingly familiar, yet somehow even more precariously built :lol:

Looks much like the "battering-ram" we built, except loose any guy wires and use two long pipes to go from the mast near the scanner to the side of the bridge near the deck level for bracing. Guy wires seems like a good option at first, but the legs worked much better. You might be able to get a main boom pole rigid enough to avoid the legs, but our setup was super light and easy to deal with compared to what I think you would need to for one rigid mast pipe. Not a mechanical engineer, so all I can share is the experience we had which is only qualitative. The data we obtained from scans like that 15' out adjacent to big gussets were exceptionally clear using a Faro 350. Could easily model every bolt and or rivet as well as other "problems."

I would share the napkin sketch of the wheeled battering ram I conjured up, but it is gone and my childlike artistry far too embarrassing. In brief it was a truss like contraption about 35' long with 15' projected from the side and ~20' of "cart" on the deck. Two 8" solid rubber wheels up front with 2 more 8" solid casters in the back. The height matched the gap between the top of the concrete barrier and the steel box tube that was added to raise the height of the barrier at some point...so about 3' tall. We had some additional weights on the back end at first, but they were not all that necessary. Like I said initially we had guy wires on a wide horizontal beam that provided some lateral bracing, and a long guy on top that was held about 1.5' higher than the main boom and secured with a manual boat winch so we could adjust the tension. Scrapped all the wires, and added the legs I spoke of. The ends of the legs were secured to the main boom with a bit of rope during transport then lowered into place after projection .Our scanner was also mounted sideways initially, which made it very easy to slide through the gap. Was very simple to use. One person could push it along the deck and project it out to perform a scan before moving on. Two people were need to lift it over the centre barrier rail, to get to the other side. Almost forgot! Get locking wheels. We used them more than we thought we would, because the ram stayed stored on-site for weeks. It was a fairly steep bridge, but it managed to not end up running away on its own becoming an actual battering ram :lol:

Sorry for all that text, a picture would be so much easier :roll:

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by sim.herrod »

We went this route a few years ago...fortunately the client supplied the vehicle (driven from Germany to UK, just for this job).

https://twitter.com/i/status/843752417984479232

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by TByers »

Scott,

We used a similar self-built arm to hangout over an unfinished elevator shaft every other floor. We had some difficulties in registration. Now I'm not sure if that's due to the lack of targets we used, or the scanner being fully upside down. All I can add is that if we were to do it again, we would have MANY more targets. We even considered in our "lessons learned" session after that we would have a few fixed targets on the ground floor to assist in a better registration process.

Good luck!!

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Re: Scanning from a Camera Boom / Boom Truck / Jig, thoughts?

Post by Scott.Warren »

sim.herrod wrote:
Thu Jan 16, 2020 8:28 pm
We went this route a few years ago...fortunately the client supplied the vehicle (driven from Germany to UK, just for this job).

https://twitter.com/i/status/843752417984479232
Great stuff! This might be an ideal solution, but seems like a unique bit of equipment.
TByers wrote:
Thu Jan 16, 2020 8:29 pm
Scott,

We used a similar self-built arm to hangout over an unfinished elevator shaft every other floor. We had some difficulties in registration. Now I'm not sure if that's due to the lack of targets we used, or the scanner being fully upside down. All I can add is that if we were to do it again, we would have MANY more targets. We even considered in our "lessons learned" session after that we would have a few fixed targets on the ground floor to assist in a better registration process.

Good luck!!
We've had trouble with scanning elevator shafts, too, so your not alone there. When we've dangled a scanner for shaft scanning, we often do a scan upright and one downwards and find that helps, in combination with what you suggested. We found with a Z+F scanner and Cyclone, the upside down scanning didn't seem to cause issues as long as we had and up and down scan for each 'dangled' scan, with a leveled high-res scan at the bottom of the shaft. Surveying up and down buildings can be a pain, leveling runs are super necessary to getting the Z portion of the control locked down.

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