Hello Mavic fans,

Today I went to fly the mavic in the canyon near by town. It's about 50m deep. There's a walkpath at around 25m above the bottom of the canyon. I had set my maximum reach altitude at 150m (swiss laws) and I had set the RH at 80m. I start flying the mavic in the canyon to reach almost the bottom of it. The mavic was about 5m above the ground taking awseome view of small water falls. When I wanted to bring back the mavic, it didn't want to go higher than about 10m. As soon as I reach 10m, I couldn't go higher and the remote was telling me: maximum flight altitude reach. However, I was actually sitting above the mavic and the mavic was well bellow the maximum reach altitude (actually the mavic was about 20m below the home point). I had to make it land on the ground of the canyon somewhere else where I could fortunatly access by walk (fortunatly, because you cannot access everywhere...but it crashed in the process). In summary:

- Max high: 150m.
- RH: 80m.
- Me: 25m above the ground.
- Mavic: stuck at 10m above the ground.

What went wrong? Does anyone have had that same issue? What should I have done to prevent that from happening. I m very hesistant now in flying my mavic below me. I'm worry it will not rise in the air eventhough it's well under the maximum flight altitude. I was lucky enough to access the bottom of the canyon, but it's not always like that.

Thank you for your help.

The Mavic calculates its altitude based on atmospheric pressure.
Is it possible that the atmospheric pressure was totally different at the bottom of that canyon?
If that is the case, then this difference could have confused the Mavic.

It's possible the Mavic can't handle negative barro. changes from home place pressure which is set before you take off.
If you had landed in the bottom of the canyon and taken of again, you may have been able to fly back to ground level.
It would be good to be able to set QNH instead of just current pressure.
This raises an interesting point about how LOW you can fly the craft. So not AGL or MSL but BGL and BSL!
I wonder how far down the Grand Canyon you could fly it?

Eric

When you were flying down into the canyon, did you notice your altitude as being negative?  The displayed altitude is  calculated relative to the barometric altitude at your starting point.  Be  sure to start on flat ground and hover a few seconds while your starting point is recorded.  

As was mentioned previously, if there is any type of pressure stratification, temperature inversion or humidity change from your starting point, it could confuse the height calculation .

One other thing:  if you're within about 30 feet from ground, VPS becomes active, and it's considered a more accurate measure of  height above ground,  Additional confusion may have been inserted if you flew near the floor of the canyon (or anywhere near the canyon wall for that matter).  May want to consider the risks and disable VPS.

First of all, thank you for your help. Much appreciate guys. First post and so many wise advice. Big TX.

@marsan: I didn't know about that. Maybe yes the pressure changed a lot.

@rotor: I couldn't land it without a crash as there were no "flat" area. I chose for a crash instead of a loss.

Sorry but what does QNH mean? Couldn't find it in the acronym list. I could fly it almost to the bottom where there's a river.

@griff: no the screen was switching from 0 to -1, like there a bug, I notice it only when it was to late.

Here a picture of the place, on the top left you can see the path way (the place where I was had no stone roof). The second pix is where I was stuck.

@rotor: I could fly is as low as about 5min from the ground (eyes guess). There were water so I didn't want to tease the devil as we say in French!

Just to verify, the GPS signal is not available or just a weak signal in the canyon, right? Please refer to the manual below:
But the drone was restricted in 10 meters as you mentioned, could you please provide the screenshot of the flight records when the prompt exists? Or please sync your flight record and provide us with your DJI account, I'll help to check. Thanks.

@thor: Yes the gps signal was weak. As i had the drone always at my view I thought it was ok.

I think it's exactly what happend is what you copy paste.

When I say 10m it's a rough guess. It could have been 5m, especially looking at the picture.

Finally i d love you to check my flight record. What should I give you? I mean what does "dji acount" means?

Thank you.

DJI Thor Posted at 2017-8-16 20:19
Just to verify, the GPS signal is not available or just a weak signal in the canyon, right? Please refer to the manual below:[view_image]
But the drone was restricted in 10 meters as you mentioned, could you please provide the screenshot of the flight records when the prompt exists? Or please sync your flight record and provide us with your DJI account, I'll help to check. Thanks.

What a blessing for us forgetful users that there is at least ONE person in the world who reads the Mavic manual...!

The worst part is that I read it. Before I use my stuff, whatever it is I read it. The mavic staid in the box 2 weeks before I used it. Maybe I should re read it

It goes now to another question. How to ride the drone when the gps s week or lost? I'll check the manual. Hehe.

That is why DJI should give us the option to switch the Mavic to ATTI mode mannualy....

Chrissy Posted at 2017-8-16 20:42
@thor: Yes the gps signal was weak. As i had the drone always at my view I thought it was ok.

I think it's exactly what happend is what you copy paste.

Thanks for the feedback, DJI account is the email account you use for DJI GO 4 app. You can sync by this route: launch DJI GO app----upper right icon ---- flight record----upper right cloud icon---- select all and start synchronization. If it is the GPS signal weak case, no worries, it is normal.  
Besides, please kindly click the "Reply" button if you need to reply me so that I can get the reminder and can deal with it asap.

DJI Thor Posted at 2017-8-17 23:30
Thanks for the feedback, DJI account is the email account you use for DJI GO 4 app. You can sync by this route: launch DJI GO app----upper right icon ---- flight record----upper right cloud icon---- select all and start synchronization. If it is the GPS signal weak case, no worries, it is normal.  
Besides, please kindly click the "Reply" button if you need to reply me so that I can get the reminder and can deal with it asap.

Thank you. I ve send you via private message my dji acount. I have snyc the flight data with my phone. I ve dowload files onto my computer. What else can I do? Thank you SOOOOOOO much for your kind help.

Chrissy Posted at 2017-8-20 02:25
Thank you. I ve send you via private message my dji acount. I have snyc the flight data with my phone. I ve dowload files onto my computer. What else can I do? Thank you SOOOOOOO much for your kind help.

Yes, I had received your account and checked your account, it happened on 16/08/2017, right? It is the case mentioned above. That is normal. And the limitation can not be removed. So we recommend flying the drone in a place with fine GPS signal. You are welcome, we also feel great if we can truly offer the help. Should you have any further questions, please feel free to contact us at any time, we're glad to help.

DJI Thor,  are the height restrictions with weak or no GPS referenced to the Home Point altitude or to the current height above ground (height above ground would require VPS / DVS operational and within operational range).  Assuming the reference was his takeoff point, he would always be below the maximum as he descended.

Chrissy, could you also upload your flight record to PhantomHelp  here and provide the link to the results.

DJI Thor Posted at 2017-8-21 00:19
Yes, I had received your account and checked your account, it happened on 16/08/2017, right? It is the case mentioned above. That is normal. And the limitation can not be removed. So we recommend flying the drone in a place with fine GPS signal. You are welcome, we also feel great if we can truly offer the help. Should you have any further questions, please feel free to contact us at any time, we're glad to help.

Thank you. I do have a few more questions (I hope it's ok).

- What should I have done once my mavick was stuck and the max altitude was reach below my home point? Was the only way to lend it somewhere and pick it up?

- Are flights below home point (according that there's strong GPS signal).

- Is there a way to "multimode" with the mavic? Like tripod+point of view (example)?

- As Griffith asked: are the height restrictions with weak or no GPS referenced to the home point altitude or to the current height abouve ground?

Thank you for your help. I appreciate.

Griffith Posted at 2017-8-21 05:08
Chrissy, could you also upload your flight record to PhantomHelp  here and provide the link to the results.

http://www.phantomhelp.com/logviewer/L7JHI0R2GID6GPCT2F0L/

Chrissy Posted at 2017-8-23 03:51
Thank you. I do have a few more questions (I hope it's ok).

- What should I have done once my mavick was stuck and the max altitude was reach below my home point? Was the only way to lend it somewhere and pick it up?

For the first question, did you mean that what to do if the RTH altitude is higher than the no GPS restricted altitude? If it is, we suggest landing the drone soon and fly in a place with a fine GPS signal if possible.
I am sorry to tell I do not quite understand your second question.
Nope, no multimode.
The restriction altitude is the relative altitude of the take off point, not the current altitude.

DJI Thor Posted at 2017-8-21 00:19
Yes, I had received your account and checked your account, it happened on 16/08/2017, right? It is the case mentioned above. That is normal. And the limitation can not be removed. So we recommend flying the drone in a place with fine GPS signal. You are welcome, we also feel great if we can truly offer the help. Should you have any further questions, please feel free to contact us at any time, we're glad to help.

So, I have had the same problem and it restricted a professional flight I was undertaking in a courtyard with weak GPS .
It seems ridiculous that there is a maximum height in these circumstances, as this could be  a factor in a large cave or the internals of a building with a tall central atrium.
The only way around seems to be switching to ATTI mode, but as this switches off all sensors the platform becomes very tricky to fly safely in such an environment and is also against most Pilots  operations manuals, as ATTI flying is not insured for.
DJI have clearly added this to restrict any flight that is not "recorded" through GPS tracking. Probably  under pressure from aviation authorities.
I would argue that this is unsafe as it only encourages pilots to fly in ATTI mode .
Please could there be a way to opt out of this, as is the case when prompted about airspace restrictions.

Dandroe Posted at 2017-9-6 15:37
So, I have had the same problem and it restricted a professional flight I was undertaking in a courtyard with weak GPS .
It seems ridiculous that there is a maximum height in these circumstances, as this could be  a factor in a large cave or the internals of a building with a tall central atrium.
The only way around seems to be switching to ATTI mode, but as this switches off all sensors the platform becomes very tricky to fly safely in such an environment and is also against most Pilots  operations manuals, as ATTI flying is not insured for.

There is no way to manually switch to ATTI mode on a Mavic, and flight height restrictions under weak or nonexistent GPS signal make this a potentially unrecoverable scenario.

Seems like if the max height restriction was based off the take-off point, then Chrissy should have been able to fly her Mavic back up out of the canyon.

Ex Machina Posted at 2017-9-6 15:50
There is no way to manually switch to ATTI mode on a Mavic, and flight height restrictions under weak or nonexistent GPS signal make this a potentially unrecoverable scenario.

Seems like if the max height restriction was based off the take-off point, then Chrissy should have been able to fly her Mavic back up out of the canyon.

Seems like if the max height restriction was based off the take-off point, then Chrissy should have been able to fly her Mavic back up out of the canyon.


Which I couldn't... the max height restriction in my case was not based on my take-off point, otherwise as you suggest I could have brought my mavic back... So I guess that when the signal is lost, the maximum height is probably what the Mavic calculate acording the his sensor (and not according to the take off point).

DJI Thor Posted at 2017-8-25 01:51
For the first question, did you mean that what to do if the RTH altitude is higher than the no GPS restricted altitude? If it is, we suggest landing the drone soon and fly in a place with a fine GPS signal if possible.
I am sorry to tell I do not quite understand your second question.
Nope, no multimode.

If I understand well, you said that the restriction altitude is the relative altitude of the take off point, not the current altitude. However, when my Mavic couldn't fly higher because it was saying "max altitude reach", I was about 5-10m below the take off point. Are you sure that the restriction altitude is not related to the current altitude? Anyway, I had it set up to 50m and I was 5m above the ground and 5m below take off point...

Hi all,

just read this item for the first time, very very interesting i must say.

But why does it stops here while there is no concensus about the height from where this limitation is calculated??

DJI Thor wrote:   The restriction altitude is the relative altitude of the take off point, not the current altitude.  So why was it not possible to raise height??

DJI Thor ??
cheers
JJB

OMG! It’s easy to lose the drone when fly down to valley. It won’t be able to come back when the GPS signal is weak down there. As the drone actually in negative high why it can’t return back to takeoff level? This sounds unreasonable and dangerous.

GDL Posted at 2018-7-4 00:59
OMG! It’s easy to lose the drone when fly down to valley. It won’t be able to come back when the GPS signal is weak down there. As the drone actually in negative high why it can’t return back to takeoff level? This sounds unreasonable and dangerous.

As long as the GPS signal isn't lost,even if you re in negative high the drone will come back just fine. But if you fly down the valley and you loose the gps,or worst even the optic mode, your drone wont fly higher than 30m high or 10m high (if i remember well)

GDL Posted at 2018-7-4 00:59
OMG! It’s easy to lose the drone when fly down to valley. It won’t be able to come back when the GPS signal is weak down there. As the drone actually in negative high why it can’t return back to takeoff level? This sounds unreasonable and dangerous.

If the drone loses GPS then how does it know it's relative height to the take of point?

Return to home relies on GPS and if the drone doesn't have GPS it falls back to OPTI modes which is limited to 10m (based on the vision system) at which point you need to land and somehow retrieve the drone.

The problem here is OP flew into a situation where the negative altitude meant OPTI would make a manual return to home impossible.

Mavic measure high by air pressure so it should know current high even lost GPS signal. Don’t understand why it can’ fly back to home level if down to negative high and lost GPS.

I have been reading through a lot of these posts but I have had a slightly different experience:

Many times, on land and on a boat, I tried taking off but after 10m , it said max altitude reached.  I had to land and take off again and sometimes it would be ok, and others it would reach that 10m height and stop again.  
Does anyone know what causes that restriction?

Is your aircraft locked on GPS mode? How many satellites it got when takeoff? Also power on the aircraft on moving platform may cause IMU and compass unable to initialise correctly.