Hi,
I'm new to all of this, so hang with me.  


I was out at a waterfall hike shooting today, and my Mavic Pro wouldn't climb over 16 ft.  I have a few theories but I'd like your opinions.

My best working theory is that I have my max drone height at 120 meters.  I was in a deep canyon and sattelite reception was poor, as was cell reception.  

The last point I had the Mavic turned on was at home, at a lower altitude.  If the Mavic couldn't update it's GPS location, and the last known altitude was a few hundred feet lower, is it possible the app retained the previous altitude as its starting altitude and wouldn't allow me to exceed my max height based on the old location where the gps signal was good?

Another theory is that it was having some sort of obstacle avoidance malfunction.  I read in the manual that 16 ft is a default height if the drone senses an object in front of the craft.  Where I took off, there were boulders in front of the drone, but enough space to take off cleanly.  

I landed and reset everything and put the drone up a 2nd time and I had the same problem.  Any ideas what could have been going on?

Thanks

Theory one will be confirmed in the app that tells you, that you have reached the max altitude. If you did not get that message, well, then your theory #1 is wrong.

How was your GPS reception in the canyon? Can you upload your logs to healthy drones and provide a link? This would tell us much more than explanations ever can.

i believe with a loss of GPS there is a max altitude reduction,  also beginner mode can restrict altitude.    ( i really wish DJI would add an Atti mode option for the C2 button)

One of the DJI forum reps (I think it was Mindy) recently pointed out that the Mavic has height restrictions when flying in ATTI and OPTI modes. I think 16ft sounds like the OPTI mode limit. Since there's no way to manually switch between these, you can force ATTI mode by disabling VPS, with the trade-off of flight stability. And naturally, neither of these modes or height restrictions would apply if you have a good GPS lock, so I assume you weren't getting GPS lock in that location.
[EDIT] Forgot to mention that I think the ATTI mode limit is 30ft.

Jason Lane Posted at 2017-1-2 06:53
One of the DJI forum reps (I think it was Mindy) recently pointed out that the Mavic has height restrictions when flying in ATTI and OPTI modes. I think 16ft sounds like the OPTI mode limit. Since there's no way to manually switch between these, you can force ATTI mode by disabling VPS, with the trade-off of flight stability. And naturally, neither of these modes or height restrictions would apply if you have a good GPS lock, so I assume you weren't getting GPS lock in that location.
[EDIT] Forgot to mention that I think the ATTI mode limit is 30ft.

I had no GPS at that location-- zero.  My log looks like a couple of 4 minute 'mystery' flights 16 ft in the air with no location data at all.  

Link to screenshots

I'm trying to figure out what happened for future reference.  It wasn't the end of the world, but I did want to get up over the waterfall and could not.  

It doesn't make much sense to me that OPTI mode won't work without GPS.  The whole point of the optical system is that it sees what GPS cannot.  
Thanks for your replies.  Just want to know what to do if I run into this situation in the future.

From the current manual on page 49:
Height is restricted to 16 feet (5 meters) when the GPS signal is weak and Downward Vision System is activated. Height is restricted to 98 feet (30 meters) when the GPS signal is weak and Downward Vision System is inactivated.

Incident Posted at 2017-1-2 09:36
From the current manual on page 49:
Height is restricted to 16 feet (5 meters) when the GPS signal is weak and Downward Vision System is activated. Height is restricted to 98 feet (30 meters) when the GPS signal is weak and Downward Vision System is inactivated.

I'd read that too.  Any clue on how to deactivate the downward vision system?  I was thinking maybe Sport Mode would be the way to shoot this next time if the GPS system fails to get a signal.

too fly Posted at 2017-1-2 09:46
I'd read that too.  Any clue on how to deactivate the downward vision system?  I was thinking maybe Sport Mode would be the way to shoot this next time if the GPS system fails to get a signal.

Pretty sure there is a setting in the App to shut that down. Not able to check on mine right now, but pretty sure it's in there.

"It doesn't make much sense to me that OPTI mode won't work without GPS.  The whole point of the optical system is that it sees what GPS cannot.  
Thanks for your replies.  Just want to know what to do if I run into this situation in the future."

OPTI mode does work (turn on), when there is no GPS, but it does have a 16' max altitude. No way around this that I see, unless you turn it off and then it will fly in ATTI mode.

too fly Posted at 2017-1-2 09:46
I'd read that too.  Any clue on how to deactivate the downward vision system?  I was thinking maybe Sport Mode would be the way to shoot this next time if the GPS system fails to get a signal.

Hello, please refer to the screenshot.

you might set something wrong, check the setting

I had this happen to me today with my M2P...  I live in a mountain canyon and like today often can not connect to more than 6 or 7 gps satellites until I can get up high enough to get past the canyon walls and connect to the required 8 or more satellites...  I don't remember having this issue with some of some of my earlier aircraft, (I1, I2 & MP) has there been a change sometime in the past with either the software or the DJI GO4 or a software update or something??  Seems like it should still be the user's decision whether to fly in gps mode or not and whether to restrict the altitude....  The suggestion above of shutting off the ground vision positioning would probably help if it lets me get up to 98', that is usually high enough for me to be able to connect to 8 or more satellites...  I'll try that tomorrow...  Thanks...