Hi Guys,

I had a little incident where the mini 2 decided somehow it was too high and took a dip into the drink.

I was watching it while it happened, taking a shot flying backwards away from us and the drone started from what looked to be about 9-10 feet altitude above the water.

My intent was to get a shot of us on the water with the drone accelerating away from us backwards, I understand that its not recommended to fly right above the water but this seemed  like it had plenty of buffer to me to stay in the air.

Here is the log
https://www.phantomhelp.com/logviewer/9WRXVW39UEODULN0FBCS/

What would have caused it to decent into the water on its own like that? I have never seen it drop more than a foot or two even on windy days on its own before

Thanks

Maybe it was hungry and saw some fish?

It's 'fish', plural btw, not 'fishes' ...

Johnny_J Posted at 9-14 07:46
Maybe it was hungry and saw some fish?

It's 'fish', plural btw, not 'fishes' ...

Thanks for the grammar check but I'm pretty sure it's correct as used.

https://idioms.thefreedictionary.com/swimming+with+the+fishes

DronesJones Posted at 9-14 08:47
Thanks for the grammar check but I'm pretty sure it's correct as used.

https://idioms.thefreedictionary.com/swimming+with+the+fishes

Fish generally refers to multiple fish of the same species. Fishes refers to multiple species. Both are correct.

Mobilehomer Posted at 9-14 08:52
Fish generally refers to multiple fish of the same species. Fishes refers to multiple species. Both are correct.

That's right, but it would be "swimming with the fishes" or "sleeping with the fishes" in TV and Movie land.

I love when a good thread heads down a rabbit hole! Or is it rabbits hole? LOL

I know that flying over grass on a hot day causes lift and wet grass causes descent.

chillibadger Posted at 9-14 10:23
I know that flying over grass on a hot day causes lift and wet grass causes descent.

I have never really noticed that before, but we are talking about 9-10 feet of un-commanded descent here, not a little bit of deviation.

I realize that at some point the IMU altitude started to read a little lower than it actually was, but I would think this would have the opposite effect and make the drone want to climb... I am a bit puzzled as to why this happened the way it did.

It's extremely well documented and tested that unstable ground and water will mess with the VPS.

Flying low over water is just generally a bad idea.

blue_canyon21 Posted at 9-14 11:08
It's extremely well documented and tested that unstable ground and water will mess with the VPS.

Flying low over water is just generally a bad idea.

Understood, however I don’t believe that 10 feet is low enough, or even that the VPS sensor is at fault here, the vps reading seems more accurate than the IMU altitude at some parts of the log.

DronesJones Posted at 9-14 10:54
I have never really noticed that before, but we are talking about 9-10 feet of un-commanded descent here, not a little bit of deviation.

I realize that at some point the IMU altitude started to read a little lower than it actually was, but I would think this would have the opposite effect and make the drone want to climb... I am a bit puzzled as to why this happened the way it did.

Hi,

Last part flying really fast backwards in Sport mode, high drone pitch up value : VPS height lost its height.....wich is not a surprise with nearly 40 degree Up pitch.
Flying VPS height at 2.5 meters above water, lost height track..
In sport mode with high drone attitude values (especially backwards) ; Mini2 has difficulty to keep height steady....
Would happen also when flying low fast backwards over land....

See my charts of your data. (see the blue and green VPS line)

cheers
JJB

JJB* Posted at 9-14 11:17
Hi,

Last part flying really fast backwards in Sport mode, high drone pitch up value : VPS height lost its height.....

Thanks for the analysis that looks a little better than the phantom help viewer.

What I don't understand though, is I launched the drone from my hand about 4 feet off the water, why is the IMU altitude showing 4.9 feet when it hits the water at 3m 9.2s ?

According to my logic, 0 feet IMU altitude should still be 4 feet off the water shouldn't it?

DronesJones Posted at 9-14 11:24
Thanks for the analysis that looks a little better than the phantom help viewer.

What I don't understand though, is I launched the drone from my hand about 4 feet off the water, why is the IMU altitude showing 4.9 feet when it hits the water at 3m 9.2s ?

Hi,

changed my view to feet...

at 3m9.2s : baro height = 5.2 feet, bottom sensor height = 2.3.
But as you see not a steady value, due to high pitch up drone angle.

Drone hits water at 3m9.1s, height 1.3 feet. (see the drone pitch/roll angels at impact)

Baro height is set to zero at takeoff, so if you let the drone steady touch the water than the baro height reads minus 4 feet, bottom sensor reads 0.0.
PS about keepin height, if i fly at 300 feet full speed forward in sport mode, sometimes i loose some height (but will be corrected in time) but as you cannot see that from large distance no one knows or mind....
Only analyzing logs will show height variations....

cheers
JJB

JJB* Posted at 9-14 11:34
Hi,

changed my view to feet...

Funny thing is I have done that shot a bunch of times, some even significantly closer to the water and never had a problem with the drone dropping altitude... At least not more than a foot or two anyways... Kinda strange that the IMU is reading positive values at the end, it should have been at 0 feet by the time it got level with our heads.

I wonder if it's worth diving for

DronesJones Posted at 9-14 12:27
Funny thing is I have done that shot a bunch of times, some even significantly closer to the water and never had a problem with the drone dropping altitude... At least not more than a foot or two anyways... Kinda strange that the IMU is reading positive values at the end, it should have been at 0 feet by the time it got level with our heads.

I wonder if it's worth diving for

Kinda strange that the IMU is reading positive values at the end, it should have been at 0 feet by the time it got level with our heads.
It's not strange at all.
Because the height you see on screen comes from measurements of changing air pressure, it's common and normal for differences of 10 feet or so over the duration of a flight.

You were flying closer to the water than you realised and couldn't see how close because you flew backwards.
Flying close to an obstacle (like the lake surface), at full speed in Sport Mode is always going to be risky.

What is considered a safe altitude then to fly over a lake? I was told 10 feet by several people so that’s obviously not quite enough then if you can’t trust the vps over water and the imu altitude is inaccurate

DronesJones Posted at 9-14 15:31
What is considered a safe altitude then to fly over a lake? I was told 10 feet by several people so that’s obviously not quite enough then if you can’t trust the vps over water and the imu altitude is inaccurate

What is considered a safe altitude then to fly over a lake? I was told 10 feet by several people so that’s obviously not quite enough then if you can’t trust the vps over water and the imu altitude is inaccurate

You can trust VPS over water, but VPS can't work properly at the tilt angle you get with full speed in Sport Mode.
There's no magic distance from water (or any obstacle) that is safe/not safe.
But if you can't see the gap between the drone and the water, and you want to backwards fly in sport mode, do it where you can clearly see the gap with your own eyes and respond accordingly.

Here is my analysis after some careful review.  You crashed your drone.  Now you just need some a bag of rices.

TonyPHX Posted at 9-14 16:45
Here is my analysis after some careful review.  You crashed your drone.  Now you just need some a bag of rices.

Haha and a scuba diver

DronesJones Posted at 9-14 16:47
Haha and a scuba diver

Long stick!!  Maybe we need a drone retrieving submarine from DJI??  : )

TonyPHX Posted at 9-14 16:54
Long stick!!  Maybe we need a drone retrieving submarine from DJI??  : )

DronesJones Posted at 9-14 15:31
What is considered a safe altitude then to fly over a lake? I was told 10 feet by several people so that’s obviously not quite enough then if you can’t trust the vps over water and the imu altitude is inaccurate

I have flown low over water many times with a mini 2. I always lower it to 5ft above water and them give it full stick forward, backward, or sideways and have been lucky I guess.

Hello there DronesJones. I am sorry for the trouble this has caused and thank you for reaching out. Since this unfortunate event happened to your DJI Mini 2, I would recommend for you to contact our DJI Support Team at https://www.dji.com/support?site=brandsite&from=nav for further assistance with regards to this matter. We will do there best to help you and give out the best resolution for the said issue. Again, I am sorry and thank you.

Mobilehomer Posted at 9-14 17:36
https://youtu.be/-BX1b6YBVP4

I think I want one of thes!

Dirty Bird Posted at 9-14 13:04
You never watched "The Godfather", where Luca Brasi was described as "sleeping with the fishes"?

Or read the bible parable :  Loaves and Fishes

I have flown over water (quite low) with the Mini 2, but never in sports mode.
Not sure if that will increase the risk of drone dipping, but thanks for the (expensive) lesson you gave me!

Montfrooij Posted at 9-15 00:29
I have flown over water (quite low) with the Mini 2, but never in sports mode.
Not sure if that will increase the risk of drone dipping, but thanks for the (expensive) lesson you gave me!

Apparently it does, I am thinking that the wind created by the speed affected the barometer, I have video of it... It suddenly just descends into the water about 8-10 feet a bit after changing to sports mode. I wish I was watching the screen and not the drone because on the video its super obvious that it started dropping, watching the drone from the boat it was not obvious at all until there was a splash.

fanse0f68750 Posted at 9-14 18:40
I have flown low over water many times with a mini 2. I always lower it to 5ft above water and them give it full stick forward, backward, or sideways and have been lucky I guess.

Me too thats why I am a little shocked this happened, I crashed my first mini due to not knowing all the flight modes properly, not understanding to wait for GPS or what ATTI mode was.. But I like to think I have been pretty careful to follow the recommendations since then and I thought the drone was sufficiently high that it wouldn't just dip into the water like that.

Mobilehomer Posted at 9-14 17:36
https://youtu.be/-BX1b6YBVP4

That is so awesome

TonyPHX Posted at 9-14 21:18
I think I want one of thes!

Here is Captain Drone's review -

chillibadger Posted at 9-15 08:11
That is so awesome

Yeah, I wish I had one for a search and rescue mission

Johnny_J Posted at 9-14 07:46
Maybe it was hungry and saw some fish?

It's 'fish', plural btw, not 'fishes' ...

Not if you're Luca Brasi.

He definitely swam with the fishes...

;-)

TCS

DronesJones Posted at 9-15 07:02
Apparently it does, I am thinking that the wind created by the speed affected the barometer, I have video of it... It suddenly just descends into the water about 8-10 feet a bit after changing to sports mode. I wish I was watching the screen and not the drone because on the video its super obvious that it started dropping, watching the drone from the boat it was not obvious at all until there was a splash.

Yeah, hindsight is always more clear.
It's a hard lesson man. And I wish we could do anything about it.
TBH, I always fly very low over water and so far that went perfect.
I do stay in normal mode and watch the screen mainly (because I usually can't see the drone).
And I know it's a risk.
But I figured I'd rather take a (calculated) risk and get some very nice footage than only fly the safest route and get the same (boring) shots as usual.

DronesJones Posted at 9-15 07:12
Me too thats why I am a little shocked this happened, I crashed my first mini due to not knowing all the flight modes properly, not understanding to wait for GPS or what ATTI mode was.. But I like to think I have been pretty careful to follow the recommendations since then and I thought the drone was sufficiently high that it wouldn't just dip into the water like that.

I thought the drone was sufficiently high that it wouldn't just dip into the water like that.
You thought that, but ......

The drone was too far away for you to see how close it was to the water.
If you had forward vision, the wideangle lens makes things appear further away than they really are.
You were flying it backwards  so you had no forward vision.
You flew at full speed in Sport Mode, very close to a big obstacle.

If you want to engage in risky flying, do it where you can see what's happening.

Yep, sports mode will make the drone lose altitude and its especially noticeable when low to the ground, what's worse is, that you were going backwards, therefore it was nose up so you couldn't see on the live view what was actually happening, I am surprised it didn't say Landing but that must be the downward sensor and water issue, i.e. it couldn't see solid ground. A shame, you need to find a local diver or club, good luck.

Bashy Posted at 9-16 04:31
Yep, sports mode will make the drone lose altitude and its especially noticeable when low to the ground, what's worse is, that you were going backwards, therefore it was nose up so you couldn't see on the live view what was actually happening, I am surprised it didn't say Landing but that must be the downward sensor and water issue, i.e. it couldn't see solid ground. A shame, you need to find a local diver or club, good luck.

Hi Bashy,

On the video it’s super obvious that it was dropping however I was watching the drone directly and not the screen, it was not nearly as obvious watching the drone as it didn’t start to drop at first until it was far enough that it looked like it was just moving backwards still.

Why not just use the dronie shots?  (canned program)

hunterws Posted at 9-16 11:02
Why not just use the dronie shots?  (canned program)

Not really the effect I was going for, I have done this shot before and it usually goes fine and looks great, focused on a subject accelerating rearwards away from it at a constant altitude

Johnny_J Posted at 9-14 07:46
Maybe it was hungry and saw some fish?

It's 'fish', plural btw, not 'fishes' ...

It's 'fish', plural btw, not 'fishes' ...

Because he did not actually use the word *fish*, you should have used asterisks rather than apostrophes.
You should have also used quotation marks rather than apostrophes (“fishes”).
A period at the end rather than "..." what have also been correct.

Class dismissed.

MBSL500 Posted at 9-17 07:43
It's 'fish', plural btw, not 'fishes' ...

Because he did not actually use the word *fish*, you should have used asterisks rather than apostrophes.

lol ok bud, you clearly missed the point on this one...