Tom Dick Harry Posted at 12-9 15:54
Despite everyone’s best efforts, I still have doubts.   Can you clarify whether the Reference System for the 120m Limit is Above Ground Level, or Above Launch Point ?   Someone stated that the drone is incapable of determining AGL, so above Launch Point applied.  This point was not clarified and the discussion went on, often with confusing interchange of the terms.

Also, the 120m Limit may be restricted to the EU, but the Reference System is most likely the same in both territories, because it is a technical parameter of the device.  Can you also clarify?

There are two height systems that run side by side
1) The legal limitations, which for the EU, are, I think, within 120m of the closest ground or, perhaps in Romania, 120m above the ground directly beneath the drone (AGL) . CHECK WHICH is applicable in Romania.
2) The height as measured by and displayed by the drone. This height is relative to the take off point, it knows NOTHING of the distance from the closest ground nor AGL.

The drone will control/limit the second system, 2) and comply with the limits set in the app by the pilot or firmware.
It is the pilot's responsibility to comply with the legal limit.

Referring to the diagram shown in the preceding post.
If you take off from the top of the hill, climb to 120m and then fly the drone horizontally towards the wind turbine, the drone complies with the 120m height that you have sent it up to and will display a height of 120m in the app but the drone will quickly break the legal limit.
To comply with the latter you would have to command the drone to descend into the legal 'layer'.

aurisoft Posted at 10-12 04:41
Never heard about it. My M4P is in EU and after first update still allows to set 500m.

I got my Mini 4 Pro last week, did the recent updates and the height is limited to 120m...

Steph Jant Posted at 12-9 23:37
I would love to be proved wrong, but I don't beleive you are right about the drone having a pressure guage.  If you are right then we have all been having a nebulus conversation for the last few months with regards to height other than that above take off position.  I also don't understand why you are trying to split hairs over AGL versus within (120m) of closest ground.  Its one and the same thing.  And even the EU diagram you included in your post references AGL

"but I don't beleive you are right about the drone having a pressure guage.  "

Oh well, not much I can do about what you believe.
But I would ask you to explain how,
1) with zero GPS signal, my drones register non-VPS height changes when flying indoors? Or
2) a drone in a plastic bag reports negative height when the bag is inflated or positive height when the air is sucked out of the bag, all with the drone sat still?
I just got an "exceeds 400ft" warning whilst sucking the air out of a bag containing an M2P and it 'descended to around -100m when blowing air into the bag.From memory I have seen the same with a mini 1 or 2.

"If you are right then we have all been having a nebulus conversation for the last few months with regards to height other than that above take off,"
Assuming you are referring to discussions about the impending EU 120m firmware ceiling, I see no reason that the means of measuring height are nebulous.

"even the EU diagram you included in your post references AGL" where? If you are referring to "which mean the AGL > 120m" that is text I added to the diagram and includes a typo I made, besides the original diagram clearly indicates (red dimension line to the extreme left ) that the AGL can be significantly greater than 120m when flying within a "within 120m of the closest ground" layer.

It's not splitting hairs to point out the difference, it is a subtle but significant difference. If my maths is correct even on a 30deg slope a "within 120m of the closest ground' rule allows 155.8m AGL.

Could dji step in and clarify the technical aspect of this issue?   I find we have some strong debaters, but we lack some basic technical information keeping this discussion tortuous.   Can dji simply clarify what reference the drone uses as ceiling height, and how it does it?   

_SoP_ Posted at 12-10 00:12
I got my Mini 4 Pro last week, did the recent updates and the height is limited to 120m...

Would you, or an other m4p owner, carry out the simple test below and report the results in this conversation?  
1- find a location having a hill higher than 120 m above launch point, and an up slope which is not too abrupt
2  set ceiling height to 120m, if not locked
3- get the drone to gently climb the slope while keeping approximately 30-50 m above ground (guesstimate).
4- report if the drone kept climbing above 120m indicated
5- Report deviations to the above procedure.

I understand this has been done hundreds of times before, but I think we need to hear the results in non-equivocal terms.

Tom Dick Harry Posted at 12-10 09:50
Could dji step in and clarify the technical aspect of this issue?   I find we have some strong debaters, but we lack some basic technical information keeping this discussion tortuous.   Can dji simply clarify what reference the drone uses as ceiling height, and how it does it?

Are you talking about how the drone measures height other that VPS height?
If so, what is there to debate?
A drone exposed to partial vacuum reports its height as increasing and, when subjected to increased pressure, reports its height as decreasing, all whilst sat still with no GPS.
Can you come up with any other explanation for that behaviour?
Try the drone in a bag experiment with zero GPS i.e. indoors or with a metal cover over the top-front of the drone, for yourself and see.

As far the achievable height, set your drone's maximum height to 70m and send it up to that height.
Once it is there reduce the maximum height setting to 25m, do not touch the throttle and watch what happens, does the drone descend to 25m?
If, by any chance, the set RTH height was greater than 25m then check what the RTH height is now set to, 25m? Now reduce the set maximum height to the minimum available, what happens the the drone and the RTH height.
Try to send the drone up above the set maximum height, can you?
If the firmware enacts a 120m ceiling in the EU then the affected drones WILL be limited to a 120m ceiling relative to the takeoff point irrespective of their horizontal distance from the home point.

The only DJI drones to break the set maximum height ceiling and the firmware ceiling have been malfunctioning drones.
I have the flight logs of around 480 troubled flights saved.
Of those, nine logs show the drone exceeding 500m by a significant amount and two of those show evidence of hacked firmware, with max height settings greater that 500m, three others might show signs of it as their logs show max height settings of 0.00.
Eight logs show the drone breaking 500m by a small amount, less that 2m, seven of those broke 500m by less than 1m, all of the eight had set ceiling heights of 499.99m. Four logs show the drone reaching 499.5m to 499.8m with set ceilings of 499.99m.

All my own flights have warned me when I was approaching the set ceiling height and from memory reduces the ascent speed, I do not think any of them have broken that ceiling by any significant amount. It would be too complicated to check the latter as I tend to set a diferent max height setting for each new location.

Hi guys, my name is Raymond.  I want to buy a m4p as my first drone, and have a concern about the flight ceiling, as the rules are tightening.  You guys are obviously knowledgeable but I see conflicting answers spreading over 6 pages, and I fear it is going to get even more complicated.  I also see that dji is not generously contributing the basic information required to keep this conversation straightforward.   
Any chance you could help me (and probably others) to answer the two simple questions I have raised above in a simple manner?  Do you know how to trigger dji participation?  In my eyes, the contribution of dji does not trow a shawdow on your knowledge, it completes it.  

Tom Dick Harry Posted at 12-10 14:12
Hi guys, my name is Raymond.  I want to buy a m4p as my first drone, and have a concern about the flight ceiling, as the rules are tightening.  You guys are obviously knowledgeable but I see conflicting answers spreading over 6 pages, and I fear it is going to get even more complicated.  I also see that dji is not generously contributing the basic information required to keep this conversation straightforward.   
Any chance you could help me (and probably others) to answer the two simple questions I have raised above in a simple manner?  Do you know how to trigger dji participation?  In my eyes, the contribution of dji does not trow a shawdow on your knowledge, it completes it.

Start a new thread entitled "Qu's 4 DJI only, drone height, measured by GPS or barometer & ......?" or similar.


In the opening post, list your questions in plain language e.g.
1) Excluding VPS sensors how does a DJI drone measure its height
2) ?? I am not sure what your precise question is but, at a guess,
''Assuming the drone is working correctly will the drone climb through either or both
.......a) the maximum height limit set, in the app, by the pilot, or
.......b) the maximum height limit in the drone's firmware ?''


and explain your reasons for wanting a definitive answer from DJI only.

Sean-bumble-bee Posted at 12-10 02:23
"but I don't beleive you are right about the drone having a pressure guage.  "

Oh well, not much I can do about what you believe.

The attached is the CsvView chart of the .DAT of the 'flight' .

Showing
the number of GPS satellites found by the drone, 0,
the drone's height & roll, it was on its side in the bag and
the prop motor speeds, 0.

Steph Jant Posted at 12-9 22:49
The definitive answer is that no matter where you fly around the world, the only reference point your drone has for altitude is from the take off position. That is because the drone does not have an altimeter.  Your drone uses GPS data to determine altitude from the take off position.  So the 120m limit used by the drone is from the take off position.

The confusion arises because some countries and regions set the maximum altitude you can fly (120m) with reference to height ‘above ground level’ (AGL).  If you fly your drone vertically from your take off position, then altitude ‘above ground level’ and altitude from take off position should coincide. But let’s say you now fly your drone up a hill or mountain slope. You might be flying legally 120m AGL, but with reference to height above take off position you could be at 200 or 300m (and you would need to adjust your max height on the RC which at the moment is to a maximum of 500m above take off position). But I would argue height restrictions should only be in relation to take off position because it’s impossible for the human eye to ‘judge’ the height of a drone above ground level

I reached out to DJI technical support and they have told me that the altitude displayed is the vertical altitude relative to the home point (which is normally your take off position but the home point can be changed) and that altitude is calculated using both GPS and a barometer.  So I was half right with my assertion and have learned something new.

That's interesting, I will need to have a look through some other logs but if you check to see if the mini 4 pro DATs from your phone or controller are readable with csvview and find that they are, produce a log's csv then have a look in that csv for a colum entitled "GPS:heightMSL[meters]" or similar.
I have had a look at a random DAT on this computer and the colum starts with what I assume is the launch point AMSL. If you play with the csv you can compare the drone's indicated 'baro' height with the indicated GPS height (recorded GPS height - launch point GPS AMSL).
I have just done this with a random log (haven't checked the drone model ) but they differed by from -6.43m to +1.83m, that's in a roughly 2 minute log.

Steph Jant Posted at 12-10 23:40
I reached out to DJI technical support and they have told me that the altitude displayed is the vertical altitude relative to the home point (which is normally your take off position but the home point can be changed) and that altitude is calculated using both GPS and a barometer.  So I was half right with my assertion and have learned something new.

Thank you Steph.  Clear and simple.  So if one hits the 120m ceiling going up a mountain, I understand from your comment that dji’s work around is to relocate one’s home point in order to keep climbing.  In your opinion , is this a realistic/practical solution?

Tom Dick Harry Posted at 12-12 01:06
Thank you Steph.  Clear and simple.  So if one hits the 120m ceiling going up a mountain, I understand from your comment that dji’s work around is to relocate one’s home point in order to keep climbing.  In your opinion , is this a realistic/practical solution?

Regarding ‘home point’, the user guide says it can be updated manually when the position of the user has changed.  So this would imply that you would have to walk to where your drone is (up the hill or mountain side) and then reset the home point.  But what I don’t know is whether your height limit is then reset.  I suspect you would have to land the drone, launch it and then you would be able to fly again to the ceiling of 120m.  Another thing to note (see page 41 of the user manual) is that if you do update the home point during flight then you will lose the ‘precision landing’ feature.  It is calibrated for the original take off (home point) position.  Also, the drone will fly back to the last home point if it loses RC connectivity or you select ‘return to home’ – so constantly updating the home point may not be such a good idea if you are on the move.

I have been flying drones for 5 years and I have never had to exceed the 120m limit.  And I do fly my drone in the alps during the winter months.  I could see scenarios where you might want to track yourself riding a bike up a hill or following a car up a mountain road and so being able to fly above 120m might be a good thing.  And another scenario might be  filming yourself hiking up a mountain - but it would make for a bloody boring video if you wanted to film yourself for 30+ minutes (the life of a battery).  So I really don’t understand some people’s obsession with the 120m limit. If people really want to fly the drone at altitude then just walk up the hill or mountain to the spot where you want to launch the drone - it will give you a good workout!
Ultimately, if the 120m limit is a dealbreaker for you I suggest you go and buy the Air 3 or one of the larger DJI drones which have more freedom when it comes to altitude - or condsider another hobby.

The 500 meters limitation is from take off right? So if i bring to a mountain that is 600 meters high, and take off from there, it can reach up to 1100 meters?

Vira9 Posted at 12-24 03:06
The 500 meters limitation is from take off right? So if i bring to a mountain that is 600 meters high, and take off from there, it can reach up to 1100 meters?

If you take off from a mountain that is 600m above sea level and you climb the drone to 500m above ground level then your drone will be 1100m above sea level. But just to be clear - the legal height limit in most countries is 120m above ground level. However, it is impossible for the human to judge height above ground level so I think the drone should be limited to 120m above take off position with no option to set 500m. Lot easier to understand!!

This is the same as limiting the speed of vehicles to 130 km/h, because that is the speed that can be driven on most roads. However, manufacturers still produce vehicles that go up to 250 km/h. I suggest that DJI remove the 120m height limit. if an individual violates this, he should be punished by the persons performing supervision. that's easy.

I'm in the UK and the max limit I can reach is 500m - this is 500m above the take-off level, so just think of it as 500m above your head.  The controller will warn you once it gets to 120m, but this is just a visual warning.  This is running the latest December firmware

Does anyone know if a 2023 activated Mini 4 Pro still can be unlocked for 500 m?

DJI doesn't write a time slot for the unlock: "Mini 4 Pro users who bought their drone before 1 January 2024 with a C0 label7 and who wish to fly higher than 120 meters from take-off point beyond 31 December 2023 can follow our Step by Step Guide below"

Stephan Jant
Following this discussion and other inputs, I find it would be great if dji could provide a way of knowing constantly the altitude above actual ground (as opposed to home point)    There is already an indicator coming up when below 10m AGL, and dji indicated the m4p contains a barometer.   I would like to open a new post on that specific topic   I would like your opinion, and your help.   

Tom Dick Harry Posted at 2-3 13:22
Stephan Jant
Following this discussion and other inputs, I find it would be great if dji could provide a way of knowing constantly the altitude above actual ground (as opposed to home point)    There is already an indicator coming up when below 10m AGL, and dji indicated the m4p contains a barometer.   I would like to open a new post on that specific topic   I would like your opinion, and your help.

How would you propose that the drone sense or determine its AGL when out of range of the downward looking sensors?
That I can think of ...
It could possibly carry a localised 3D map in its memory and then calculate its AGL based its current location, the launch location and the height above the launch point but what would what cost in terms of storage space/memory and calculation power ?
Alternatively, would you want to pay for more powerful IR emitters or alternative wavelength emitters so that the sensors have the range to read from what.....400ft or more ?