Mavic 3 Pro training flight... Working the POI

New England Droning · May 16, 2023

I took my Mavic 3 Pro out to play with different settings like the POI... I've only had the Mini2 so this is new for me.

First I realize being over water is a known issue and some of what I saw may be due to that. First off, the winds were challenging. 17mph with gusts to 30mph but I didn't really lose positioning laterally only in altitude. I was watching the drone more than the camera or I might have been more scared...

but the water was churned up so there was no mirror reflection to throw off the downward sensors. (I thought the wind pushing laterally would be the bigger issue)
Anyway, I was working on choosing the right POI settings, and looking up I saw that I was losing alt quickly and I gave it the order to climb which it did.
I did a 360 pano and once again it underperformed (messed up) and I don't know if it is the lack of reference points or an actual problem.
but during the auto Pano, it did the same thing where it lost 10-12ft in altitude and got to within 10ft of the surface.

Yes, I had about 22 sats before I took off and a solid home point lock.

I need to try a park and see if it is water doing this (I shoot along the ocean a lot)

So I need to figure out if this is me being a NUB or does the M3P have some bugs to work out.
Also, the POI seemed to break the lock on the lighthouse and I've never had active track/POI before so it's probably just me but in watching the youtube videos they gave it much more challenging subjects that were moving. My lighthouse was stationary and it would wander off and lose it...

Thoughts?

You can view the video of this portion of the flight to see how close it came to getting a bath...
Another good reason to keep eyeballs on your drone and not the screen (Vlos)
I don't see a way to put videos on here...

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Dave Maine · May 17, 2023

Constant altitude is an issue with all the drones I have flown. The root cause is the fact that DJI uses a barometric altimeter that isn't particularly accurate or good. It is integrated into the overall FMS which is what flies the drone. This reading will change as the locations barometric pressure does continuously, sometimes so slightly, and sometimes quite dramatically.

To guess your next question, the GPS readings are quite accurate in the ground plane dimensions (+- 16 ft, 95% of the time), but far less accurate in the vertical direction. The barometric altimeter was selected by DJI, probably because their testing gave better overall results. It would have been cheaper for them to not use a barometric altimeter at all.

New England Droning · May 17, 2023

Thanks Dave, and I'm fairly comfortable with the drone characteristics but I'm used to my mini 2 and after 2 years I've seen small dips 1-3 feet at most in windy conditions (9-20).
But what I witnessed was a loss of altitude from just a bit higher than the Winter Island Lighthouse (Aprox 30' high) and I wasn't looking at the screen but eyes on the drone and it dropped to a height of approx 10ft (the flight profile says it was 18ft) above the water before I stepped in and gave it full left stick up to climb back up.
As I dig in on the RC under profile, I'm watching the replay where I canceled the pano it says just prior it went from 11m down to 6m (uncommanded during an auto pano) and that is when I decided to step in and give full throttle up to 12m.
I was also making my first attempt at doing the automated POI and a couple of times it would work for a bit and then break lock and would head off on its own.
Needless to say when I have a calm day I will take it out again to try this again.

GadgetGuy · May 17, 2023

Dave Maine said:
Constant altitude is an issue with all the drones I have flown. The root cause is the fact that DJI uses a barometric altimeter that isn't particularly accurate or good. It is integrated into the overall FMS which is what flies the drone. This reading will change as the locations barometric pressure does continuously, sometimes so slightly, and sometimes quite dramatically.

To guess your next question, the GPS readings are quite accurate in the ground plane dimensions (+- 16 ft, 95% of the time), but far less accurate in the vertical direction. The barometric altimeter was selected by DJI, probably because their testing gave better overall results. It would have been cheaper for them to not use a barometric altimeter at all.

Within some 20-30 feet of the ground the optical and radar sensors below take over, and display their much more accurate elevation measures in true AGL as a separate number. However, highly reflective surfaces such as moving water, with surf and waves, produce unreliable results, and the displayed AGL elevation cannot be relied upon under those circumstances.