Dronelink crashed my drone! Altitude error on Terrain Follow at take off. Please help!
I'm making a 3D map at a school site in the lower Himalaya. I've made them before and used terrain follow (AGL) where there is a lot of altitude change - as otherwise I can't get enough resolution.
My first map mission here with a fixed altitude worked fine. But as soon as I set the altitude to Terrain Follow (AGL), the drone took off, hovered at 1m, as it does but then instead of zipping up and off to the start point, instead it dropped 50cm and flew directly into a pile of bricks 5 metres away. Miraculously the camera was not struck but the rest of the drone is a mess.
I made a new map as a test, it again worked fine with the altitude referencing the home point, and again dropped to 50cm and would have crashed had I not been ready.
Can anyone tell me what is going on? As I need to make a high resolution map and have only one more day. If I see the altitude to the reference point, I'm too low or too high as soon as I'm a few metres away from my home point.
Pleas help! Thanks
Justin
Mavic Air2S
iPhone 12 Pro
Comments
19 comments
Did you run the verification mission before ?
Hi
Actually I didn't.. I ran it for the fixed height one...
So I see on the preview that it is trying to start at the lowest point. And so going horizontally straight and then down... Why does it not realise that it has to go up to 50m first before moving horizontally? Surely this would be the same anywhere? Moving just off ground level is going to hit obstacles anywhere.....
If I move it to begin at the highest point this may fix the initial problem - but what if the battery runs out while it's at one of the low points. It will return to home, then try to return to that low point and do the same thing (move horizontally just off ground level)
Also - Pausing missions never seems to work for me, so I can't voluntarily stop it at a high point bring it home to change the battery and then relaunch....
What should I do?
Thanks for the quick reply. Much appreciated
Can you post a link to the mission, so that we can take a look at it
https://app.dronelink.com/justin-wickham/my-first-project/plan/lRrWgKpN2rgRTh40Y3GI
Hi Martin - link above. The problem seems to have been that I had set the start point at edge of the map with the lowest altitude - and the drone wanted to head directly there (without ascending first to clear buildings/trees etc).
It's raining at the moment (Monsoon here) so I haven't even able to test now that I have moved the start point to the high altitude edge of the map. But I presume this may fix the initial problem. But what happens if I need a battery change when the drone is back in low altitude territory. If it acts in the same way it will return to base fine, but then crash while trying to return to the low point..
Mission link above. Any thoughts greatly appreciated.
Warmest
Justin
hi Justin, that looks good, what I do at the start of missions or after battery changes is fly to a safe height before I start/restart the mission, also make sure you've got a good satellite count before launching
In these types of situations, it is always safest to manually fly to the start or resume point before engaging the mission.
I think it is a bit more complicated than that. For example, if you took off on one side of a ridge and wanted to start the map on the otherwide (below the ridge), even if the drone ascended to the altitude of the start location, it might still be below the ridge during the approach. In the end, verifying the mission ahead of time in the preview is critical, and it may require manual intervention to complete the entire mission safely as you have seen. I think the final solution is really to allow terrain follow during the approaches and while resuming, but this feature does not exist yet.
Thanks both. I didn't realise I could manually fly back and resume from an in the air starting point!
I still think it would make sense on all automated missions for the drone to ascend to a designated height first (auto set to 50m perhaps) before going anywhere. But much appreciate both your feedback. And thanks for being so fast with it too:) Really appreciated.
Happy flying!
J
Yeah one of the places I regularly fly at my starting point is near some floodlights and also a tall tree so I manually ascend tool I'm above them till launching a mission, this also gives me a chance to see how the drone is handling if there's a bit of a breeze
Your question: I still think it would make sense on all automated missions for the drone to ascend to a designated height first (auto set to 50m perhaps) before going anywhere.
It does always ascend up first. Look at the mission planner. The Issue is you have the approach going all the way out to the actual map start and it doesn’t follow the terrain while on approach as Jim stated. Suggest using a much shorter approach to the start of map. Then it will follow the terrain. Just a thought. Enjoy….
I think he has since changed the plan. There are cases where it can do what he describes.
🤙🏼 Okey dokie…
Sorry for not understanding all the details you give. However ... before starting any mission I analyze the simulation and (sometimes) run the verification mission.
My question is twofold :
1 - Did Justin apply these 2 advices ?
2 - Was it possible to anticipate and avoid the crash by doing so ?
Thx
Short of the possible issues in some cases, I’d still use a short approach then add a path using AGL markers along that section to the map n this plan The very steep incline and at 164 feet is showing in some areas it is fairly close to the ground. I’m Not a mapping pilot but usually see about 250’ or higher for the pilots who do 2D and 3D maps. Just some suggestions for future flights with this plan. So many ways to set up plans and it comes down to what works for your specific situation. Good luck Justin….
After three years, any update on the addition of terrain follow for approaches and resuming? I just narrowly missed crashing for the same reason on resuming a large mapping mission after a battery swap. I thought I'd missed a setting, but it appears the only solution is for me to include a manual checklist step to fly manually when resuming/approaching.
Thanks,
John
The solution is to use waypoints with AGL instead of a checkpoint.
Hmm, I'm not sure what that means. This was for a map plan using terrain follow. The issue was upon resuming the mission after a battery swap, and the resume position was lower than takeoff point. I avoided a crash (albeit narrowly :)), and proceeded by manually flying close to the resume point (as suggested above). Ideally, this would either use terrain follow during approach/resume, or ascend to minimum safe altitude and traverse before descending to resume point.
In this case, I don't see how I would use waypoints or checkpoints.
Sorry, for resuming there is no solution (besides flying it manually).
Yeah, I understand. I'm just adding my voice to prioritizing this.
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