Well, I was recently looking at buying a 3D scanner (the CR-Scan Ferret) to speed up the 3D modeling process for model locomotives and the like. Something that I thought about were the potential inconveniences and impracticalities of trying to scan a full-sized locomotive, due to the large size. I was, therefore, wondering about the possibility of mounting a 3D scanner on a drone, which, I suspect, would make scanning a locomotive much easier and faster. A quick search of Amazon turned up this drone: https://www.amazon.com/Control-Headless-Quadcopter-Altitude-Birthday/dp/B0F8N2L39H/ref=sr_1_5?refinements=p_72%3A1248963011&rnid=1248961011 . However, as someone who has neither a 3D scanner or a drone (excepting one of those stunt drones, but that doesn’t really count), I was wondering if someone here had tried this or maybe if there were any possible issues. I did think of a few while I was here, though.
Obviously, weight is a potential issue. The Ferret is supposed to weigh about 105 grams, which equates to about .24 pounds. Since I was unable to find any specification on what kind of payload that drone can carry, it’s uncertain if it would even be able to lift the scanner or have a reliable flight pattern with it. Another possible issue is whether the drone would be stable enough for the scanner to work well, for that matter. Additionally, the flight time of the drone could be a constraint as well.
Scanning a full sized locomotive ? 
I think the most important thing is going to be the computer though
As for the drone, I honestly don’t know. I think the scanner is going to have some pretty big difficulties to follow the movement though
Well, I wouldn’t be the first to use a scanner on a real train.
A computer would be a problem, so one potential solution would be to make a customized drone with a built-in scanner, exceptional stability, and a computer installed in it. That ain’t happening anytime soon. However, if I remember correctly, the Ferret can work with a phone and that might be light enough.
I have seen some pretty stable drones, but I don’t know exactly how stable it has to be…
Use a telescoping painters pole with a tripod adapter on the end - I do this to make high-resolution 3D models of rock outcrops for archaeological studies. You can also just use drone images taken with lots of overlaping (50%) to scan the train - then use appropriate software to create a point cloud from it, works great for large things!
Well, there’s another option (or two)…
The way the ferret and other NIR scanners work is by throwing an infrared dot mesh on the part that needs to be scanned. This ranges the typical distance that you get shown in Creality Design space while scanning.
Mounting it on a drone won’t work. There are drone 3D scanners but these are usually LiDAR scanners that cost $15000 or more, DJI offers one for their drones.