Hello, I flew my drone about 10 meters to the spillway of a lake.  Initially Tripod worked perfectly, the drone was slow and smooth.  Then I popped it down behind the spill way and probably it was too close, a few feet, and began to go forward.  I immediately popped it up and then went to navigate it back behind the wall.  This time I think the problem was that it became level with the water and from the movie it was mostly seeing the water, it then went crazy moving around rapidly in an area of a few feet.


At this stage it was under a foot bridge so I couldn't go up, and within a few seconds it was crashed into a bush.  This was rather fortunate in retrospect as if it had hit the concrete it would have been damaged, but it seems ok except for a few small notches in the propellers.  I turned it off and restarted, it reset its inertial sensor and then took off normally and responded to controls, so I landed it.

I checked the bridge today to see if there is a power cable in it, uncertain.   

I'm generally happy with the Mavic Pro, it is a factory refurbished model.  There are a couple of other issues, that day I noticed it was drifting a bit in light winds on P mode.  Shouldn't happen.  I had to move it away from a bush.  Another time it dropped out of GPS mode in strong winds and blew away.   Fortunately I was able to quickly point it in the right direction and bring it home.  I couldn't get it to do its dronie the last time I flew it, so checked the firmware, and reinstalled the remote firmware which was up to date.  There had been a message of inconsistent firmware, that day.

I've put the video online here:  https://www.youtube.com/watch?v=G_eHxtZU_Wc

Aloha Davo,



Aloha and Drone On!

Hi Davo,

Would be great help if you upload your flightlog,
using this link > https://www.phantomhelp.com/LogViewer/Upload/

Flightlog will tell what happend.

cheers
JJB

Hi Davo, I am sorry to hear about the accident. As the drone had had a crash, I would suggest that you send in the drone for an overall diagnosis. Data analysis will also be provided if the drone is under the warranty period. Please contact our support at http://www.dji.com/support to start a case.  

I think the problem was that it became level with the water and from the movie it was mostly seeing the water, it then went crazy moving around rapidly in an area of a few feet.
Seeing water doesn't cause your Mavic to do anything crazy.
The cause of your incident is something unrelated.
Post data and can you tell what was the surface you launched from?

JJB* Posted at 3-17 01:09
Hi Davo,

Would be great help if you upload your flightlog,

https://www.phantomhelp.com/LogViewer/63ZY3W7K1ESO1LRBNBG2/

It appears there was a compass error.  Thanks very much.

Was the foot bridge made of metal?

Labroides Posted at 3-17 03:08
I think the problem was that it became level with the water and from the movie it was mostly seeing the water, it then went crazy moving around rapidly in an area of a few feet.
Seeing water doesn't cause your Mavic to do anything crazy.
The cause of your incident is something unrelated.

thanks, but just from Googling there are lots of posts that it can do that   https://forum.dji.com/thread-126458-1-1.html  However from uploading the flight record

eg:  "flying over water becomes dangerous only at low altitude - below 15Meters when video and ultrasonic sensors are activated. water reflection and waves produce erroneous distance reading from the ground (water in our case) Although the MP is at 8 meters in the air the sensors may mistakenly indicate that you are at 2 meters or vice versa .. at 14 meters. This immediately leads to processor error flight MP .... and CRASH!"

compass error appears to be the problem, so there must have been a power cable in the foot bridge as I suspected.

DJI Thor Posted at 3-17 02:13
Hi Davo, I am sorry to hear about the accident. As the drone had had a crash, I would suggest that you send in the drone for an overall diagnosis. Data analysis will also be provided if the drone is under the warranty period. Please contact our support at http://www.dji.com/support to start a case.

Thanks very much Thor.   I must also add that I had a very productive day prior to this incident, completed a  video project I was working on.  I'll fly it some more, I have only had it since January, and if there are other issues I'll take it up with Support, but I think its OK for the moment.

DavoDownUnder Posted at 3-17 04:31
Thanks very much Thor.   I must also add that I had a very productive day prior to this incident, completed a  video project I was working on.  I'll fly it some more, I have only had it since January, and if there are other issues I'll take it up with Support, but I think its OK for the moment.

You were way too low I cant tell where you actually flew this from but you cant fly that low over water without turning off the sensors. It generates random height and positional information.

It looks like it got a collision alert as you approached the wall and it auto backed off and then you reacted the wrong way and flew it into the tree.

The compass error are irrelevant It will fly fine without the compass as long as you don't invoke RTH.

DavoDownUnder Posted at 3-17 04:26
thanks, but just from Googling there are lots of posts that it can do that   https://forum.dji.com/thread-126458-1-1.html  However from uploading the flight record

eg:  "flying over water becomes dangerous only at low altitude - below 15Meters when video and ultrasonic sensors are activated. water reflection and waves produce erroneous distance reading from the ground (water in our case) Although the MP is at 8 meters in the air the sensors may mistakenly indicate that you are at 2 meters or vice versa .. at 14 meters. This immediately leads to processor error flight MP .... and CRASH!"

but just from Googling there are lots of posts that it can do that  
There are lots of posts that are complete nonsense.
Your drone won't fly crazy because the snnsors detect water.

so there must have been a power cable in the foot bridge as I suspected
It doesn't take a power cable.
All it would take is a bolt or some steel framing close to the compass/

Denny-R Posted at 3-17 04:23
Was the foot bridge made of metal?

It has metal girders but also on one side they are boxed in with wood, so possibly a cable here.

Labroides Posted at 3-17 04:46
but just from Googling there are lots of posts that it can do that  
There are lots of posts that are complete nonsense.
Your drone won't fly crazy because the snnsors detect water.

I did post the link for JJB, here it is:  https://www.phantomhelp.com/LogViewer/63ZY3W7K1ESO1LRBNBG2/

No way of knowing if there was reinforcement, the lake was constructed in 1929.  There are steel girders on each side of the bridge.

I think the gist of the water theory was if you turned of the sensors you would not have a problem, or just fly at a reasonable height.  Anyhow, that is clearly not the cause as the Compass error shows in the flight log.   However the compass error occurs during the flight, not at take off.

Labroides Posted at 3-17 04:46
but just from Googling there are lots of posts that it can do that  
There are lots of posts that are complete nonsense.
Your drone won't fly crazy because the snnsors detect water.

DJI have a warning and recommendation on flying close to the water surface. The Optical flow tracking and IR sensor. Activates at low level and overrides the GPS and Altimeter. There are a n umber of old Videos that demonstrate this issue. After these DJI offical released a warning on water low level overflights.

Now that the OP has posted where it went crazy as he says it has wooden beams and water between. That would have messed up the flow tracking.

DavoDownUnder Posted at 3-17 04:55
I did post the link for JJB, here it is:  https://www.phantomhelp.com/LogViewer/63ZY3W7K1ESO1LRBNBG2/

No way of knowing if there was reinforcement, the lake was constructed in 1929.  There are steel girders on each side of the bridge.

What did you launch from?
If it was it a wooden deck, how far was your drone from any bolts or steelwork?
Which way was your drone pointing when you launched?  Was it NW?

Forget the nonsense about sebnsors and water.
That had nothing to do with your flight.

bjr981s Posted at 3-17 04:44
You were way too low I cant tell where you actually flew this from but you cant fly that low over water without turning off the sensors. It generates random height and positional information.

It looks like it got a collision alert as you approached the wall and it auto backed off and then you reacted the wrong way and flew it into the tree.

Hi Thor,  I didn't fly that low over the water, it was about 2 metres  and then when I got to the wall I lowered it.  Initially it flew toward the wall as you can see in the video, I did not do that, but luckily I was able to just fly up.  When it went into the high speed circling motion it was back several feet from the water but the perspective seems like it was right up against it from the camera view.  I was not flying it at this stage just gently nudging it around then it took off in this circling motion far faster than it should have in Tripod mode.  There were only seconds to respond.

I might have nudged it to the wrong direction because the drone was facing me.  I suppose there is a reason DJI supplies spare propellers in the fly more option.  It is expected you will crash.  I have had quite a few tense moments flying, I have survived them.  This could have been a lot worse if it hit the concrete at speed or ended up in the lake.  Another learning experience.

My objective was do do a "reveal shot", flying up from behind the wall to reveal the lake.  Lesson learned stay well away from objects.  The week before I flew it through a gap in a soccer net, had to go backwards because the forward sensors didn't like it.  That success led to this incident.

DavoDownUnder Posted at 3-17 04:55
I did post the link for JJB, here it is:  https://www.phantomhelp.com/LogViewer/63ZY3W7K1ESO1LRBNBG2/

No way of knowing if there was reinforcement, the lake was constructed in 1929.  There are steel girders on each side of the bridge.

Hi Davo,

First ; flying low over water is in general no problem, only flowing 'rough' water has sometimes effect on the sensors.
I fly alot over water in my country, never had a problem (just be carefull if flying at 0.5 meter ; not to apply 100% down for short time ; will go into autolanding *...)

* if autolanding protection is ON.
In your log few times a CompassErrorLarge, and an Compass error

At the end, at 1m53s all input to zero, but craft did not hover in postion. distance fluctuating from 13.0 to 13.7 to 11.8 meters.At the same time in the log a compass error.

So for this 'crash' the compass is highly suspected.

AFAIK flying close to -  or flying over iron constructions can cause a compass error like this.


cheers
JJB

Thanks, most appreciated.

DavoDownUnder Posted at 3-17 16:28
Thanks, most appreciated.

That looks like Daylesford to me. Flying back under the partial shadow of the bridge could have caused a lack of GPS signal, and also, the wall will most certainly contain steel re-inforcing that would affect the compass.

DavoDownUnder Posted at 3-17 04:31
Thanks very much Thor.   I must also add that I had a very productive day prior to this incident, completed a  video project I was working on.  I'll fly it some more, I have only had it since January, and if there are other issues I'll take it up with Support, but I think its OK for the moment.

Thank you for getting back, to ensure the flight performance, sending in for diagnosis is recommended.
And it is suggested flying in open areas, large metal or tall structures may affect the accuracy of the onboard compass and GPS system. Flying over the bodies of water is not recommended. Thanks.

I fly low over water very often.
Very low.
50cm or so.
The only problem I sometimes have is that the drone thinks it is too low and decides to pull up.

PS, I'm also flying the MP

Geebax Posted at 3-17 16:43
That looks like Daylesford to me. Flying back under the partial shadow of the bridge could have caused a lack of GPS signal, and also, the wall will most certainly contain steel re-inforcing that would affect the compass.

Yes, Daylesford Lake.

Montfrooij Posted at 3-18 00:22
PS, I'm also flying the MP

I won't be rushing to try low flying over water, but it could give some excellent images.  People have reported their drone tried to land on the water, and on that basis I've kept to at least several metres height.  When I've had more use from the drone I'll be a little more reckless and also pilot skill will be better.  I have some reservations about Tripod mode now, I think it might tax the drone's computer possibly crashing it with overloaded data.  Newer drones have better 3D computation, lot of work going on with driverless vehicles as well, so should flow through to new generation drones.  Very happy with my purchase of the Mavic Pro all the same, was going to get the Mini glad I got something better.  Thanks for your comments.

DavoDownUnder Posted at 3-18 05:25
I won't be rushing to try low flying over water, but it could give some excellent images.  People have reported their drone tried to land on the water, and on that basis I've kept to at least several metres height.  When I've had more use from the drone I'll be a little more reckless and also pilot skill will be better.  I have some reservations about Tripod mode now, I think it might tax the drone's computer possibly crashing it with overloaded data.  Newer drones have better 3D computation, lot of work going on with driverless vehicles as well, so should flow through to new generation drones.  Very happy with my purchase of the Mavic Pro all the same, was going to get the Mini glad I got something better.  Thanks for your comments.

I have some reservations about Tripod mode now, I think it might tax the drone's computer possibly crashing it with overloaded data.
All that Tripod mode does is to slow down the joystick response and max speeds.
It doesn't make any additional computational requirements.
But whenever you are close to an obstacle, it doesn't take much for it all to end badly.

DavoDownUnder Posted at 3-18 05:25
I won't be rushing to try low flying over water, but it could give some excellent images.  People have reported their drone tried to land on the water, and on that basis I've kept to at least several metres height.  When I've had more use from the drone I'll be a little more reckless and also pilot skill will be better.  I have some reservations about Tripod mode now, I think it might tax the drone's computer possibly crashing it with overloaded data.  Newer drones have better 3D computation, lot of work going on with driverless vehicles as well, so should flow through to new generation drones.  Very happy with my purchase of the Mavic Pro all the same, was going to get the Mini glad I got something better.  Thanks for your comments.

I never use tripod mode.
I however did adjust the EXP and GAIN to have better control in the first part of the stick motion.
I think I flew at least 10km over water below 1m.
I did disable the obstacle sensors (because I want to be in control and it improves stability as far as I have noticed)

Montfrooij Posted at 3-18 05:46
I never use tripod mode.
I however did adjust the EXP and GAIN to have better control in the first part of the stick motion.
I think I flew at least 10km over water below 1m.

I think it becomes possible to fly over the water because you disabled the sensors.  I watched quite a few videos on adjusting settings, not all correct in my opinion.  I think if you over do it it can take longer to stop the drone, which could cause problems.  Do you get any spray off the water flying that low?

DavoDownUnder Posted at 3-18 22:36
I think it becomes possible to fly over the water because you disabled the sensors.  I watched quite a few videos on adjusting settings, not all correct in my opinion.  I think if you over do it it can take longer to stop the drone, which could cause problems.  Do you get any spray off the water flying that low?

I don't like tripod mode exactly for that.
I almost flew the drone into a tree when I tried that mode.
I have made curves in my stick settings so the first part is very sensitive, moving to unsensitive.
That way I can react fast when I need to and fly slow when I want.

No problem with spray. The drone's airflow is not that strong.
I wanted to fly very fast and low backwards to get this nice moving water....
But it turned out it is hard to film the downdraft when you are +1m flying backwards.
Only when the gimbal was facing down enough I could get that effect.

DavoDownUnder Posted at 3-18 22:36
I think it becomes possible to fly over the water because you disabled the sensors.  I watched quite a few videos on adjusting settings, not all correct in my opinion.  I think if you over do it it can take longer to stop the drone, which could cause problems.  Do you get any spray off the water flying that low?

PS, I do fly responsible, but I do sometimes try other stuff because I want a certain shot.
Nothing dangerous for other people, maybe only for my drone.
I first tried a lot of flights in normal height over water, getting a bit lower every time.
After that I was confident I could make a try at very low altitude.
The MP behaved good, except for it wanted to raise height a couple of times (but that is not a risk, just not good for the shot)

No worries.  I have finished the video I was working on, I have another lake project but every time I go there the wind has been too strong.  Hopefully we get some of those still autumn days soon.