Best drone for measuring accuracy of steel beams on construction site?

[MNewman]

I was recently asked what drone one should use for the highest accuracy to measure steel beams on a construction sight as it would save a company quite a lot of money from sending a person up there to measure it themselves. I figured I would forward that question here.

The research I have found has unearthed things like LiDAR and Photogrammetry. One website says they're equally accurate. Another says that LiDAR is better. And then ChatGPT says Photogrammetry is better.

That said, are they referring to accuracy when mapping an entire region or accuracy when photographing steel beams up close?
And any recommendations for what drone/drone package would do the trick for accomplishing this task?

 

[Cafguy]

I used to Erect structural steel for a living.
My first question would be: Does your local government not have a building Dept.? in their archives exists a copy of the blueprints used to Erect that steel. If not they DO have the Engineering companies info.
You would need to do more than "measure" the steel, You would need thicknesses as well to be accurate.
You can get sort of a good idea of the sizes by attaching a bright ruler to something and then taking a picture. use the ruler as a measurement guide. It is only semi accurate tho.
For work such as yours and I am assuming Engineering of some kind,.....Sorry, but a good latter or scissor lift and a tape measure is the best most accurate way. There are always archived Blueprints but you must know that during construction a minor change or 2 might have been made and not noted. SO your back to going out there and getting dirty.
If you get yourself a "span" table for structural steel beams it will be a great help to you...Go to your local steel supplier and ask for one.

 

[MNewman]

I'm not an engineer. I'm a drone pilot. An engineer who works as a project manager for an elevator company asked me the above, so I'm going to assume that he already has the blueprints necessary and all that stuff. Sometimes, parts are cut incorrectly -- by as little as an inch or less.

While measuring it by hand may be the most accurate way, that doesn't mean it's the safest or most cost efficient -- hence why he's asking if it's possible to send a drone to go up to do it rather than a person.

 

[MS Coast]

I can't imagine any of the drones discussed on this forum being able to do beam measurements on on a construction site on any but the very grossest level.

 

[Cafguy]

It would be a nice thing but with drone photos you would just be guessing.
Their is a big list of things people wish they could do "simply" with a drone that turns out just wont work. Its not cost effective at all! really I mean if there is a doubt, You will be back at the site Again with a latter and a tape measure anyway..
I would say doing it with a drone Photo only will only be as accurate as whomever is examining them is experienced in Structural steel and even then its a guess.
You certainly wont be able to tell if one bay is actually 1 or two inches more or less than another with a photograph that's for sure.
Having erected steel for some time, I really don't see much use for Drones (except maybe,Flying Larry back the Spud wrench he just dropped!! Again! (too risky)
P.S. If you do this do it on a Sunday, Ironworkers tend to be a little "nasty" if you try and fly Drones around them while they are working.lol

 

[MNewman]

I can't imagine any of the drones discussed on this forum being able to do beam measurements on on a construction site on any but the very grossest level.

What about the Matrice 350RTK or the DJI Mavic 3 Enterprise with RTK Module?

 

[MS Coast]

What about the Matrice 350RTK or the DJI Mavic 3 Enterprise with RTK Module?

There's no forum here dedicated to the Matrice series. The Mavic 3E with RTK is probably the most capable of the models addressed here, but would it be able to provide measurements on a 50' or so beam to <1" accuracy?

 

[Meta4]

An engineer who works as a project manager for an elevator company asked me the above

Ask the project manager if he has ever heard of such a thing being done with a drone.
If he has, get details from him.
It sounds very much like it's not something that would be possible.

 

[Cafguy]

How much money do you want to spend!? YES a Matrice along with an RTK and also plenty of GPC's would do it Thats kinda like buying a rolls royce because you dont like walking tho. LOL
Maybe:
Take a photo of the steel frame with your drone or however you wish. place 2- 1' rulers on the steel in a cross. Go back to the office and insert the photo into AutoCAD. Draw a 1'x1, cross, Using zoom and your eyes Scale the drawing using the rulers in the photo to "scale to your 1' lines. Still not accurate but with the two rulers and inserting into AutoCAD you can draw lines on top of the pics and determine measurements (for beam size you still need thicknesses tho.

 

[DARKSeifer]

Any drone can do it, even a Mini 2. Just set the timer on the drone to take a pic every two seconds and manually fly around to cover everything, the closer you are to the subject the more accurate and detailed the final geometry will be (polygons or pixels per cm). Then you process the images through Metashape (the best photogrammetry software quality wise) using depth maps instead of point cloud, and that's basically the best possible way to do it today.

Precision will depend on the control points you set on the scene and the scale, as optical distortion and rolling shutter is corrected/discarded by the software and the mean value of thousands of pics as you clean the preliminary point cloud to be left only with the most precise points.

What you are paying is basically automation on the flight, the mechanical shutter so you can fly the drone at higher speeds while taking photos without getting rolling shutter and the RTK module for higher precision in autonomous data gathering and control point setting.

The Matrice 4E should be the best to do the job with it's 4/3 sensor with mechanical shutter, RTK module and the ability to make gross 3D reconstructions on the controller itself to plan autonomous missions right in the site.

Photogrammetry precision has no limits, it all depends on the magnification of the pics and the scale and resolution of the final 3D model. The thing is to find which resolution is enough for any given scenario.

 

[MNewman]

Any drone can do it, even a Mini 2. Just set the timer on the drone to take a pic every two seconds and manually fly around to cover everything, the closer you are to the subject the more accurate and detailed the final geometry will be (polygons or pixels per cm). Then you process the images through Metashape (the best photogrammetry software quality wise) using depth maps instead of point cloud, and that's basically the best possible way to do it today.

Precision will depend on the control points you set on the scene and the scale, as optical distortion and rolling shutter is corrected/discarded by the software and the mean value of thousands of pics as you clean the preliminary point cloud to be left only with the most precise points.

What you are paying is basically automation on the flight, the mechanical shutter so you can fly the drone at higher speeds while taking photos without getting rolling shutter and the RTK module for higher precision in autonomous data gathering and control point setting.

The Matrice 4E should be the best to do the job with it's 4/3 sensor with mechanical shutter, RTK module and the ability to make gross 3D reconstructions on the controller itself to plan autonomous missions right in the site.

Photogrammetry precision has no limits, it all depends on the magnification of the pics and the scale and resolution of the final 3D model. The thing is to find which resolution is enough for any given scenario.

Gotcha. Well in this case, it's about being accurate for elevators on a construction site. My understanding is that the elevator company wants to make sure that the parts they are going to install for the elevator shaft are the right size, so they want to make sure they have the absolute precise measurements for the steel beams and frames that have already been constructed so as not to insert a part that is either too long or too short -- even by 1 inch.

Now I'm new to this kind of drone work (I've only really used it to market real estate houses before), so forgive me if these questions seem obvious. Would the only way be to get an accurate measurement be for the drone to scan the entire building in order to make a 3D model, or could I just focus on the part where the elevator is?

If any drone can do it, why spend far more on the Matrice 4E? Just for ease of use?

 

[Cafguy]

they want to make sure they have the absolute precise measurements for the steel beams and frames that have already been constructed so as not to insert a part that is either too long or too short -- even by 1 inch.

This is because beam profiles vary by beam weight. The inside distance between the two flanges of say a W12x15 beam and a W12x32 beam will be much different. Thicker beams also have more "round Angle" and therefore less room to place equipment flat on the web surface.
Beams are represented by Depth x weight (The W means Wide flange), A beam of higher weight and (therefore more span or load capabilities) will have less distance between the flanges of the beam on the inside. The elevators equipment must fit inside the Flanges. not forgetting r.
You need Thicknesses...eseses lol

 

[Meta4]

Now I'm new to this kind of drone work (I've only really used it to market real estate houses before), so forgive me if these questions seem obvious. Would the only way be to get an accurate measurement be for the drone to scan the entire building in order to make a 3D model, or could I just focus on the part where the elevator is?

If it can be done the way you are considering (and that's highly unlikely), the task would require a specialist operator.
Someone experienced in detailed technical engineering inspections.
It's going to need someone with more than experience in real estate drone photos.

You should tell the project manager that it's probably not possible and that you aren't qualified or experienced enough.

 

[Rchawks]

Part 107?? This would not be under recreational.

 

[IronSky1]

My daytime real job is Physical Infrastructure engineering for data centers . Recently a company came in and scanned the floor plans of one of our buildings. Ridiculous you will never get any accuracy with drones flying in industrial facilities. As CafGuy said thats what engineering drawings are for.

 

[MARK (LI)]

It sounds like it would be quicker and more accurate to just send 2 guys up with a tape measure, a note pad and a pencil....maybe more fun with a drone, but it seems like it would be difficult to avoid structural members already in place.....forget about VLOS

 

[Cafguy]

Part 107?? This would not be under recreational.

Any Flight you make that is not for "recreation" is a part 107 flight.
Now suppose your hobby is examining steel structures with your Drone, wouldnt that be recreation.....lol ( the IRS would disagree lol)

 

[PepperBird]

There's no forum here dedicated to the Matrice series. The Mavic 3E with RTK is probably the most capable of the models addressed here, but would it be able to provide measurements on a 50' or so beam to <1" accuracy?

Try DJI Matrice Drone Forum

 

[MS Coast]

Try DJI Matrice Drone Forum

Yes, it's a separate entity, not part of mavicpilots.com.

 

[Hill Peaceman]

LiDAR is the most accurate in any case. Photos will give better results for rendering the textures(for now) what you do not need in your case.