Hi,
Flying my Mavic Mini today it didn't want to go higher than around 20m.  There was an error message on the screen, but in the sun I couldn't read what it was.  Looking at EXIF from the photos, the highest photos had a GPS altitude of 117m, which would correspond with a 20m height above takeoff which is just under 100m ASL. The max altitude in my settings is 120m which corresponds to the legal limit in the UK, but this is supposed to be height above the surface, not above sea level.  Do the various altitudes set in the DJI app in fact refer to altitude ASL rather than height?  If they do then clearly I need to set my max to 220m, and re-adjust it each time I fly from another location.  Same with the RTH altitude, which at the moment would be 70m underground.

Thanks, Tony

When flying your drone, the reference altitude is at the Home Pont.  If you're at 100m ASL and you set RTH height to 50m, the drone will attain that height (unless it is already higher)and return home at 50m above Home Point or 150m ASL in your case. !20m AG is the UK legal limit, but that is relative to the point where the drone might fly to. For example, if you fly up a hill from your take-off point you can achieve 120m above the hilltop.Always best to leave a margin for error though.

Are you certain the ceiling was a 20m and not 30m?
There are various height limits imposed depending on whether or not GPS  is available and or if VPS is available, these are detailed in the manual.
https://dl.djicdn.com/downloads/ ... Manual_v1.2_enI.pdf

There may also be height limits imposed if you are not logged into the App but I am uncertain about that so you would need to google it.
As Bleriot53 says the drone has no knowledge of its ASL  and is concerned with only its height above the level of the take off point.

However, I would draw to your attention the fact that wind speeds tend to increase with height above the ground. As such setting a height limit of 400ft and presumably using it, is perhaps unwise. For flat land flights my max height, with any drone is normally under 60m, I mix units a lot.
The mavic Mini is not the best drone in wind.
Equally, unnecessarily high RTH's run the risk of putting a Mavic Mini up into high wind, they also waste battery power in the ascent and most noticably, if you are battery watching, in the descent. My normal RTH height is 25m to 30m, to avoid trees.

BE VERY CAREFUL when setting height and distance limits in the FLY app, it is VERY easy to accidentally change one when setting another, I know this from practical experience.

Looking at EXIF from the photos, the highest photos had a GPS altitude of 117m, which would correspond with a 20m height above takeoff which is just under 100m ASL.
Forget the "GPS altitude" because it's meaningless and doesn't come from GPS despite the label.
It can commonly be out by +/- 200 feet or more.

Do the various altitudes set in the DJI app in fact refer to altitude ASL rather than height?
All heights for the drone relate to height above the launch point.
So you don't need to set my max to 220m, and re-adjust it each time I fly from another location.

There was an error message on the screen, but in the sun I couldn't read what it was.  
If you want to find out what actually caused your issue, the recorded flight data is the place to look.
Go to: https://www.phantomhelp.com/LogViewer/Upload/
... where you'll find instructions.
That will give a report you can post a link for the report here.
Or just post the .txt file.

Thanks. I should have guessed that the EXIF altitude was meaningless, if I'd thought for even a couple of seconds, because we're actually nearer 190m ASL here. It's a shame though, and I wonder why they'd bother putting in meaningless altitude data instead of the real figures.

Anyway that log viewer shows exactly what issue I'm hitting, just before hitting the apparent ceiling there's a logged message "DFlight altitude restricted. Log in or go to real-name authentication." Searching for that shows a lot of people finding this problem, and a lot of different and some contradictory ways of working round it. Plenty of suggestions for me to try anyway.

And you were right, it was 30m rather than 20m. Again from the log "Max altitude reached (Altitude limit 30 m)".  And the "IMU Altitude" which started at zero maxxed out at just under 100 feet.

It solved another mystery as well, the drone's apparent unwillingness to go forwards at one point. Researching this limit, and looking at the plot shows exactly what was happening there as well.  It looks like it was hitting the 50m horizontal distance and the plot clearly the path curving at what must be a 50m radius from takeoff.

By the way, what is "real-name authentication"?

Newflinder Posted at 8-8 07:22
By the way, what is "real-name authentication"?

Absolutely no idea.

Typing that brought to mind Spike's "Absolutely no idea " from Nottinghill lol
https://getyarn.io/yarn-clip/c8e19fef-379c-425f-9987-d17b6ecbeda1

Strange the things that stick in our minds lol, that looks to be the correct clip but I can no longer hear is

Newflinder Posted at 8-8 07:17
Thanks. I should have guessed that the EXIF altitude was meaningless, if I'd thought for even a couple of seconds, because we're actually nearer 190m ASL here. It's a shame though, and I wonder why they'd bother putting in meaningless altitude data instead of the real figures.

Anyway that log viewer shows exactly what issue I'm hitting, just before hitting the apparent ceiling there's a logged message "DFlight altitude restricted. Log in or go to real-name authentication." Searching for that shows a lot of people finding this problem, and a lot of different and some contradictory ways of working round it. Plenty of suggestions for me to try anyway.

To get past the 50/30 limit, try signing out of your DJI account and signing in again

I should have guessed that the EXIF altitude was meaningless
Actually there are two altitudes in the image metadata.
The one that DJI label as GPS height, is read by a lot of software as Absolute Height and it's no use.
But the other is labelled as Relative Height and that's the height you see on your screen.
Some software won't read the complete metadata.

Thanks, the trouble with the sign out and back in suggestion, is it's only possible if there's an Internet connection. IE typically not possible if you're out and about.  I've done it back home which might do the trick, but I seem plenty of people suggesting that the phone needs to be in "airplane mode" to stop the app even trying to verify the account. Hopefully one or the other method will do the trick.

Regarding EXIF my photo software shows the following altitude related values, these are just grabbed from a random photo yesterday.  GPS lat and long look correct, but not altitude ..

    Altitude Ref    Sea level
    GPS Altitude    118.13


    drone-dji:AbsoluteAltitude    +118.13
    drone-dji:RelativeAltitude    +29.90


Assuming all these are in metres the last one pretty much correlates with the flight data which shows IMU altitude of around 98'.

Newflinder Posted at 8-10 08:51
Thanks, the trouble with the sign out and back in suggestion, is it's only possible if there's an Internet connection. IE typically not possible if you're out and about.  I've done it back home which might do the trick, but I seem plenty of people suggesting that the phone needs to be in "airplane mode" to stop the app even trying to verify the account. Hopefully one or the other method will do the trick.

Regarding EXIF my photo software shows the following altitude related values, these are just grabbed from a random photo yesterday.  GPS lat and long look correct, but not altitude ..

the trouble with the sign out and back in suggestion, is it's only possible if there's an Internet connection.
Once you are signed in, you should be fine for a long, long time.
Just check after any app updates.

I seem plenty of people suggesting that the phone needs to be in "airplane mode" to stop the app even trying to verify the account.
Airplane mode or not makes no difference.

Assuming all these are in metres the last one pretty much correlates with the flight data which shows IMU altitude of around 98'.
Exif heights are metres.
Here's an example of why I said that the Absolute Altitude is useless.
Although the DJI label says GPS height, it actually comes from an interpolation of the atmospheric pressure.
DJI's algorithm fails to account for air pressure varying and the Absolute Altitude can be out by +/- 200 feet or more.
I have a hunch that the drone wasn't 265 ft below sea level when I shot this.