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Precision landing works some of the time??

dixiefla

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I have tried landing the drone automatically over and over on one of the standard circular bright orange Honga landing pads. Most of the time it does great. But about 1 out of 4 or 5 tries, it lands off the pad, usually about 3 to 15 feet. Today, it landed spot on 4 times and once about 4 feet away. Yesterday, in an entirely different area, it landed on the pad 3 times but once tried to land on top of my pool cage 30 ft away.

Each session I make sure to update the home spot, and get confirmation; then I read somewhere that it helps to ascend vertically 7 meters and hesitate for a few seconds to allow the unit to survey the helipad surroundings. So I do that each flight. The smart controller is about 10 ft from the pad each time, no magnetic interference, no signal or GPS problems, etc. I have the latest updates; I use the RTH feature and have it start about 100 ft altitude, to avoid any trees, etc.

I emailed DJI tech support and in a prompt reply they said don't use RTH to home point, use RTH to controller (pilot). Which means, land manually every flight. I can easily do that by using RTH to controller or by cancelling RTH when it gets close, but this defeats the whole purpose of the precision landing feature, which is a very nice feature that I would like to use.

Why would it get it right most of the time and then be way off on another flight, a few minutes later, same day, same location, same conditions??
 
Just to make sure ... below highlighted from the user manual is observed?

2020-01-15_19-01-38.jpg
 
I saw those but they don't apply. I use RTH when the aircraft is hundreds of feet away from the pad. I do not use the "RTH at current altitude" option because the "currect" altitude could be 30 ft or whatever, and this might cause it to crash into trees on the way nome. So instead I set a RTH altitude of 110 feet, and this works fine, brings it home over all possible obstructions. Its the precise landing on the pad which is the issue. With nothing changed, how can it "miss" 1 out of 4 or 5 times?
 
I myself have a Mavic Air ... occasionally it can miss the "spot" from a precision take off by 4-8ft. Usually it's very precise ... a bit the same scenario as you describes. Used precision take off & landing a lot in the beginning but now a days I usually stick-start the drone & fly it home, trust myself more then the automation ;)
 
I had an similar experience with RTH recently that may, or may not, offer a possible explanation. I flew a few hundred feet away and just for the hell of it pressed the RTH button (since I had only tried it once before where it worked perfect) and watched as my M2P flew dutifully toward the home point only to land about 6 ft away from my home made landing pad of a square piece of white plastic with a duct tape X on it. I stood there and said Huh, why did it do that. After a short ponder I realized that there were several shadows from the surrounding 150ft tall trees overlaying my landing pad. Being an ex engineer, and after thinking about it later, I did some calculations about how far the shadow moved since I took off and low and behold it was in the ballpark. I am thinking that the larger pattern of the shadows fooled the drone. When I get the chance, I will try to recreate and prove this theory.
 
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I had an similar experience with RTH recently that may, or may not, offer a possible explanation. I flew a few hundred feet away and just for the hell of it pressed the RTH button (since I had only tried it once before where it worked perfect) and watched as my M2P flew dutifully toward the home point only to land about 6 ft away from my home made landing pad of a square piece of white plastic with a duct tape X on it. I stood there and said Huh, why did it do that. After a short ponder I realized that there were several shadows from the surrounding 150ft tall trees overlaying my landing pad. Being an ex engineer, and after thinking about it later, I did some calculations about how far the shadow moved since I took off and low and behold it was in the ballpark. I am thinking that the larger pattern of the shadows fooled the drone. When I get the chance, I will try to recreate and prove this theory.
Shouldn't deny that it can be a possible explanation ... unfortunately it have happened me on an overcasted day in the middle of a field without actually anything more the my orange landing pad to "memorize". Perhaps it can be several reasons for it to miss ..?
 
I have had the same issues, it happens now and again. The most annoying one is when the drone lands half on half off the landing mat.
 
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I have had the same issues, it happens now and again. The most annoying one is when the drone lands half on half off the landing mat. That part in the manual about landing where the drone is if it is within 5 metres of the take off point is a bit of a safety concern, it should land where it took off from. I don’t understand why it would do that when it can RTH if it was 6 metres away.
I argued that point: too many if this then that. I was flamed for it.
 
Make sure your downward facing cameras are clean and that Precision Landing is turned on.
There's no option to turn on/off PL on the M2. The condition is if you took off vertically high enough before flying out, and there's enough contrast on the ground to visually acquire the landing spot.
 
For what it is worth my view would be that it is to do with the accuracy of the GPS. It is rarely spot on even with 16 stations.
That's the reason for PL. Once it is in the neighborhood based on GPS, it uses visioning to fine tune the landing spot.
Before PL was added to M2, it tended to be off by about 5 feet.
 
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As a comparison, my Yuneec Typhoon H (drone of year at 2017 CES) offers accuracy within 25 feet. That works great on a 4-lane highway. Not so much near trees. My M2P is a quantum leap better.
That's the reason for PL. Once it is in the neighborhood based on GPS, it uses visioning to fine tune the landing spot.
Before PL was added to M2, it tended to be off by about 5 feet.
 
I've Mavic 2 Zoom and its precision landing rate is 100%. I use Orange/blue circular H written helipad and it lands perfectly with 1" or 0.5" accuracy...

Make sure, you do vertical take-off up to 30m. Then move towards your target filming area. This is my practice and it is very successful.

All options related to sensors are ON in the settings.... like Obstacle, downward vision positioning...
 
When the landing spot was off, did you guys see the message "Precision Landing Correcting Landing Position" ?

1579278938172.png

In this flight precision landing did not take place. The message did not show up :

 
Thanks for all the input, guys. I agree there is no way to "turn precision landing on or off". I used the method suggested in the manual, to ascend vertically right above the landing pad to 7 m and hover there for a few seconds, to allow it to "see" the surroundings. I'll try the suggestion to ascend straight up to 30m, maybe that will help, altho that's pretty high, and it would seem the lower altitude would allow it to fix the landing spot more precisely than at high altitude. Obviously, it is easy to land manually, but this PL is a nice feature and its a kick to see it land spot on by itself.
 
Thanks for all the input, guys. I agree there is no way to "turn precision landing on or off". I used the method suggested in the manual, to ascend vertically right above the landing pad to 7 m and hover there for a few seconds, to allow it to "see" the surroundings. I'll try the suggestion to ascend straight up to 30m, maybe that will help...
My earlier post about turning precision landing off was based on a MP. I need to get better at recognizing that different models have different features.

I think the units of measurement have been mixed up. 30ft is commonly used in the US which would be closer to 10m. 30m would be too high for a fix. According to the M2 manual your 7m is correct. The interesting thing is the manual does not mention a pause.

1579281862351.png
 
Yeah, 7-10 meters makes sense. I just assumed the pause is good, maybe not necessary. But I still have the problem of missing the pad once every 4-5 times even when doing this, with nothing changed.
 
Please accept my apologies..
I mistakenly wrote 30m..it is actually 30 feet

Sorry again
 

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