This is a question coming from a nervous and relatively new flier. I fly for a construction site and we have just reached the point of having cranes on the job. I would usually fly at 74m altitude but the cranes exceed this and I need to still fly for progress reports.
I don’t want to fly higher as it will lose quality/ for safety. We have an M3E and Obstacle Avoidance is on, but I still worry about colliding with the cranes.
Does anyone have any experience with this type of situation and what would you recommend?
We have 6 cranes on a 60 acre site ranging from 130ft to to 340ft AGL. You really don’t have a choice but to fly higher for safe operations but if you are not so concerned with Survey-grade you can fly lower oblique flights looking at key areas of interest that do need more detail. If you are flying an M3E you are not going to lose much accuracy, more so resolutions which I think is what you may be more concerned with and those lower obliques will help. Make sure that you are facing as perpendicular to the subject as possible and use tripod mode at around 4m/s with a 1-2 second interval to make sure you are capturing quality data.
Are you using RTK/PPK?
Don’t forget that side OA is not that great so if you are crab-walking make sure you look down the line first and utilize the OA cameras during the traverse. Even if you have to stop to take a look and then restart.
Thank you for the response Michael!
Good to know we won’t be losing too much even if we flew higher. It’s my first job operating a Drone taking over for someone else, so I have been very cautious about how to safely navigate the issue.
We currently fly using one main map to capture the whole site and implement a couple of panoramas and photos as well for progress. I’ll try to go and adjust the settings now to higher altitude, lower the gimbal, check the sides and lower the speed for when we fly the map plan.
We use RTK here if that helps!
Thank you so much for the advice, I really appreciate it.
RTK should be mandatory at this point IMO. Just to clarify the high flight should be nadir and then run some facade-like patterns in tripod mode with a 45-65d gimbal. Same to you!
I fly a site with 6 cranes and had to adjust as when I started documenting they only had 2. It is a bit unnerving, just make sure you higher. Ask the crane operators if necessary or the PM and/or just fly your drone up from where you are going to launch and see what height you come up with. VERY IMPORTANT Be sure to take into account that where you launch on a job site may differ greatly. Choose a spot and stick with it. Make sure you test your altitude from the same place you are always going to launch. If you take off in an area that is lower then where you normally fly from it might give you a heart attack depending on how close you are. Really want to skip a heart beat, look at the ortho photos being taken when it is over the cranes. You will swear it is inches away. GULP!
Couldn’t agree more. I just flew a large plant (200ac) with 32 cranes yesterday with 2 of them being at 400ft so I had to break into 4 plans on the fly. Man do we need exclusion zones! Anyways, my full-time site has 4 buildings and 7 cranes. Tallest being 345ft to tip of flag so we fly at 375ft and supplement critical areas with low oblique imagery. Another important not is to give them at least 30ft of clearance. This isn’t as unnerving with an RTK drone but a non-RTK can easily float 5ft in space.
Yes going from a site with very few mobile cranes to very tall towers is very scary! We changed our flight plans from 60m to 110m now just to have a lot more leeway away from the cranes. Thankfully we’ve picked a good spot that is higher than the main site area so we should always have a distance from the cranes, but I tense up every time the drone flies around them and triple check the controller and the drone to make sure it won’t crash!
Thank you for the tips as well!
Thank you for the helpful advice once again! I’d be terrified having to fly around your job! I’ll try to keep the 30ft in mind, even though our drone RTK I always want to be high enough just in case! Exclusion zones are a great idea. Good luck with that job, how scary!
I cut mapping for the M3E at sustained 20mph and all flight at 30mph depending on how gusty it is. The M300/350 can perform normal flight in more but mapping is all about stability so 20mph sustained with gust of 40mph is not the greatest idea. My experience has been that it’s not just the flight of the drone itself, but gusts will blow the gimbal around and cause all kinds of problems.
Not looking for absolute accuracy where every point is in relation to the rest of the world, but going for say relative accuracy like shooting a volumetric pile…
Shooting with a high resolution of around 1.5cm/px and decent overlap with say 4 passes over a fairly narrow beach 300’ or less, obtaining a true elevation point to be used later for calibrating the map, can we expect decent output to show topographical characteristics i.e. good elevation points, which could then be put into the appropriate software by a surveyor for modeling and measuring?
In this case we are not using GCPs, and the maps would be in 1-mile increments.
I was told anything over 7 miles and you have to take into account curvature of the earth, not to mention BVLOS issues, laws etc.
You could get very good results if you were using RTK/PPK, but without it or GCP’s I don’t think it will be very usable. If you were doing something like a small 10 acre tract, then there are calibrations that you can do to get the results somewhat consistent but in corridor mapping without GCP’s you’re going to get warping and twist that you can’t control. One thing you can do to combat it is to fly just a little higher and do a cross hatch. Not parallel and 90° to the water, but at an angle. This will help the software calibrate the cameras better. Just run less overlap on each flight and 2cm/px. Maybe something like 70/60 instead of 80/65. Make sure each segment/setup has at least 5-6 images of overlap.
Oh, and curvature of the Earth can break Survey-grade tolerances at 3 miles.
