Drone updated to latest firmware today and I took it for a test flight around the cottage. House is located on a pretty steep hill with a lake 100+ steps (feet?) down to it. I took off from the house and tried to fly down to the dock, however as I approached (altitude reporting something like -2.3m) the mini slowed its descent and then announced "Landing!" while still 50-60ft in the air. I immediatly countered with a climb control input which cancelled the landing. I tried several times and only once did I manage to get down to the altitute I intended (no, I didn't want to land on the dock!)
Is there some setting somewhere that allows the mini to fly below its take-off altitude? Why would the mini think it was going to land when it was still several dozen feet in the air? Now, I was over a frozen, freshly snow covered (read: visually featureless directly below) lake, so perhaps the VPS thought it was seeing the ground right below it?? Is there a way to override auto-landing and still allow the mini to descend? (Other than taping over the sensor, which I don't really consider an option). Now perhaps I could have let it continue its descent to get lower and then just cancel when I got low enough, however - I didn't want to risk it dropping out of the air and landing on the (mostly) frozen lake as I had no intention to trek out there to get it if it did!!

Any feedback would be appreciated. Thanks.

I'm not sure about what happened with your situation, and you may already know this, but the altitude is based off the take off point. So when you went below the take off point, that produced the negative value in altitude. Whether or not that has to do with what happened in your case, I'm not sure. I know I've taken off from a mountain side and decended to around -75 feet without issue, but that was prior to the .004 update. You might post your flight log so we can see if we can figure this out.

Is there some setting somewhere that allows the mini to fly below its take-off altitude?
No special setting is required.
Just like a real plane, your drone can fly higher or lower than the launch point.

I guess my question is: What triggers the "Mode changed to Confirm_Landing" in the mini. Is it solely based on VPS interpreted data? Or does altitude influence the mini's decision to "land".

Yes.  That's the point.  Of course the AC hardware can fly below its launch point.  But only if the firmware/software allows it.  If flying below the launch point triggers an auto landing, effectively, we cannot fly the drone below its launch point unless we want to crash.

There are many situations when we might want to take off at a higher elevation than where we will be flying.  There are some very picturesque canyons near me that are only accessible from the canyon rim unless one has a boat or technical climbing expertise and equipment.

smellyspice Posted at 12-31 14:27
I guess my question is: What triggers the "Mode changed to Confirm_Landing" in the mini. Is it solely based on VPS interpreted data? Or does altitude influence the mini's decision to "land".

It might be VPS related.
Altitude makes no difference.
Just as the drone can fly higher and lower than it was launched, it can land on higher and lower ground.
DJI's design engineers understand that the earth is not completely flat.

So we come back to the OP's original question.  Why did his drone attempt to auto-land when he tried to fly below the take-off point using the new software?

That's the question.  Does the new firmware/software have a bug that caused this?  If so, that's scary, and needs to be addressed ASAP.

It would be nice to see the flight log on this one I think

So I've PM'ed the logs to JodyB and we've been chatting out-of-band. I can see in the logs where, prior to the mini initiating auto-land, I did in fact have full down-stick. So this explains why auto-land was being initiated. During my initial descent, I was not full down stick, but each time I saw the mini slow its descent, I increased down-stick because I was clearly higher than the ground (still at tree top level) - my full down-stick input was to get the mini moving downward! So this brings us back to the VPS just being confused over the featureless ground and just refusing to go lower because of it, except to land. It would be nice if VPS data was included in the log - so we would know for sure. Maybe it is, but I don't see it in the airdata or phantomhelp data display.

I'll do a few more tests, but now that I've looked at the data, I'm pretty sure the bird is acting as it should.

Hi. I am sorry for the trouble this has caused. I am happy to know that your query was answered by our valued DJI members. If you have further inquiry or concern, please feel free to post it here at DJI Forum. We are here to help and thank you for your valued support.

smellyspice Posted at 1-1 08:58
So I've PM'ed the logs to JodyB and we've been chatting out-of-band. I can see in the logs where, prior to the mini initiating auto-land, I did in fact have full down-stick. So this explains why auto-land was being initiated. During my initial descent, I was not full down stick, but each time I saw the mini slow its descent, I increased down-stick because I was clearly higher than the ground (still at tree top level) - my full down-stick input was to get the mini moving downward! So this brings us back to the VPS just being confused over the featureless ground and just refusing to go lower because of it, except to land. It would be nice if VPS data was included in the log - so we would know for sure. Maybe it is, but I don't see it in the airdata or phantomhelp data display.

I'll do a few more tests, but now that I've looked at the data, I'm pretty sure the bird is acting as it should.

Well, that's good to know.  While it's handy to be able to force a landing using full down on the left stick, I can also see how trying to lose altitude needs to be done very carefully or that could be interpreted as wanting to initiate a landing when you're really just struggling to fly downward.

It would be nice if the RC had a soft stop for the left stick such that you could pull it down against that stop to get maximum downward power without initiating a landing.  If you want a landing, you pull the stick down past that stop, or something like that.  It's sort of a dangerous user interface setup the way it is.

There may have been a strong updraft that you were fighting near the rim of the valley, and that made it difficult to descend right there.  I can see me doing exactly what you did, too.  So this is a good warning for us all to be careful when using downward stick!

Thank you for coming back to this thread to post your conclusions!  I need to keep that in mind when flying.

smellyspice Posted at 1-1 08:58
So I've PM'ed the logs to JodyB and we've been chatting out-of-band. I can see in the logs where, prior to the mini initiating auto-land, I did in fact have full down-stick. So this explains why auto-land was being initiated. During my initial descent, I was not full down stick, but each time I saw the mini slow its descent, I increased down-stick because I was clearly higher than the ground (still at tree top level) - my full down-stick input was to get the mini moving downward! So this brings us back to the VPS just being confused over the featureless ground and just refusing to go lower because of it, except to land. It would be nice if VPS data was included in the log - so we would know for sure. Maybe it is, but I don't see it in the airdata or phantomhelp data display.

I'll do a few more tests, but now that I've looked at the data, I'm pretty sure the bird is acting as it should.

I did in fact have full down-stick. So this explains why auto-land was being initiated.
It doesn't explain anything.
If full down stick initiates autoland with the Mini, it's the only DJI drone that works that way.
When up in the air, full down stick should do nothing except allow you to descend at max descent speed.

It would be nice if VPS data was included in the log - so we would know for sure. Maybe it is, but I don't see it in the airdata or phantomhelp data display.
There's plenty more data available in the Phantomhelp report than you are aware of.
Post the link.

Looking at the recorded data from this flight I see .....

The drone appeared to be flying and responding to your joystick input properly.
You descended and climbed a number of times.
At 8:33 you descended to -16.8 metres proving that the drone could descend well below 2-3 metres.
You flew more and at 12:41.3 you gave it full down on the left stick.
The drone resisted and stayed at 2.3 metres, but at 12:42.8 Forced Landing was initiated and the drone slowly descended.

Looking deep into the data, I see the VPS sensor underneath the drone is recording heights above what it perceives to be below it.
At launch it is registering as 0.1 metre.
At 12:16.2 it registered 9.3m and you descended from there.
At 12:26.8 it reached 2.6 metres
At 12:42.7 it was showing 0.4 metres above something.
As the Forced Landing proceeded and the drone went lower, it got to 0.2m at 12:44.4.
But at 12:44.5 it changed to 1.9m and at 12:45.3 it was back to showing 0.1m and 0m shortly after at the end of the flight data.

I looks like the VPS was being confused and getting a false height reading from the surface below it.
There are a number of conditions and surfaces that can confuse the VPS sensors and these are described in the manual.

Labroides Posted at 1-1 18:55
Looking at the recorded data from this flight I see .....

The drone appeared to be flying and responding to your joystick input properly.

I have not flown since the update but my home is on a hill above the water. I will test it somewhere not near the water tomorrow. I had not had any issue to date with any of my other drones flying below takeoff height. So it's troubling to me that it would force land. Hate to say it but hoping it's a sensor error or something like Labroides said.

Labroides Posted at 1-1 13:39
I did in fact have full down-stick. So this explains why auto-land was being initiated.
It doesn't explain anything.
If full down stick initiates autoland with the Mini, it's the only DJI drone that works that way.

In controller mode 2, full down on the left stick with the Mini does initiate a forced landing if you hold it down for a certain length of time.

However, it may be that it only does this when the downward-looking sensors tell the drone that there's something directly, and close, below it.

I normally land the Mini by holding the left stick down.  Getting to the display on my phone and touching the exact right place, then locating, touching, and holding the little confirmation icon is cumbersome.  And it requires taking my eyes off of the drone itself to refocus on the phone display.

So I normally land by using the left stick down method because it's safer and more convenient most of the time.

But again, this may only work when the drone is low, such that the downward-looking sensors see that the drone is quite low, with the left-stick-down "command" overriding the drone's normal tendency to rise up when it detects something directly below it.

As you point out, there may have been some confusion in the drone, where the downward-looking sensors thought that the drone was near a safe landing surface, AND the left stick was being held down - so it landed.

Maybe snow or trees just under it at the wrong moment, etc., fooled it into thinking it would be safe to land.

Sigmo Posted at 1-1 19:40
In controller mode 2, full down on the left stick with the Mini does initiate a forced landing if you hold it down for a certain length of time.

However, it may be that it only does this when the downward-looking sensors tell the drone that there's something directly, and close, below it.

It will only auto-land on full stick down once it detects (or thinks it detects) the "ground" at a set distance below, otherwise it'll just descend at "full throttle" never initiating auto land.

JeremyFr79 Posted at 1-1 19:51
It will only auto-land on full stick down once it detects (or thinks it detects) the "ground" at a set distance below, otherwise it'll just descend at "full throttle" never initiating auto land.

That's what I thought.  It will normally rise up to avoid an obstacle below it, but if you give it full down on the left stick,and hold it down, while it's detecting the close-by "ground", then it will initiate a landing.  That's how people land the drone on their hand, etc.

In the OP's case, I wonder if the snow-covered pond below the drone fooled the downward vision sensors, and it decided that it was close to the ground, and he wanted it to land.

That's what we're all thinking, I believe.

Labroides Posted at 1-1 18:55
Looking at the recorded data from this flight I see .....

The drone appeared to be flying and responding to your joystick input properly.

Thanks for the analysis. Once I saw my full stick down input, I suspected it was the VPS as mentioned above.

Here is a video showing a bit of what I was doing and what the VPS had to deal with:


There is a reason why the Mavic Mini's specs say:  "Operating Environment: Non-reflective, discernible surfaces"!

BTW - Which column in the CSV file shows the VPS altitude? I didn't notice it in the airdata csv export, but looking briefly at the phantomhelp csv, there is a ton more data there. Which is odd, since the raw data used to create that report came from an airdata export!!

They do warn about snow.  But darn, it's just so nice to be able to fly when it's snowy outside.  I guess we'll just have to be careful about full-down on the stick when flying over snowy areas, because I fully intend to do it again myself... and often!  

Nice house, too!  

smellyspice Posted at 1-1 20:09
Thanks for the analysis. Once I saw my full stick down input, I suspected it was the VPS as mentioned above.

Here is a video showing a bit of what I was doing and what the VPS had to deal with:

Answering my own question: VPS column in CSV: OSD.sWaveHeight [m]

Sigmo Posted at 1-1 20:43
They do warn about snow.  But darn, it's just so nice to be able to fly when it's snowy outside.  I guess we'll just have to be careful about full-down on the stick when flying over snowy areas, because I fully intend to do it again myself... and often!  

Nice house, too!

LOL - thanks. Yeah, this is likely a rare circumstance - Snow stopped falling less than 24 hours before, it was solid overcast, so no shadows - AND - I wanted to try and fly down to the dock.

I wonder how long the mini would descend to land before it either gave up and turned off the motors and dropped to the ground. What would have happened if I let it continue to descend and just cancel it when it got "low enough" (based on my forward view on the camera. It was a long snowy walk to the dock, so I didn't want to find out! Any volunteers!?

smellyspice Posted at 1-1 20:54
LOL - thanks. Yeah, this is likely a rare circumstance - Snow stopped falling less than 24 hours before, it was solid overcast, so no shadows - AND - I wanted to try and fly down to the dock.

I wonder how long the mini would descend to land before it either gave up and turned off the motors and dropped to the ground. What would have happened if I let it continue to descend and just cancel it when it got "low enough" (based on my forward view on the camera. It was a long snowy walk to the dock, so I didn't want to find out! Any volunteers!?

Yeah.  Snow, with an overcast sky is almost featureless!  We need ski goggles to fit over the downward sensors on these Minis to help them see better over snow.

I guess that wouldn't help its sensors, but the human eye has its best discrimination for variations in brightness in the yellow part of the spectrum.  That's why ski goggles are yellow.  It's amazing how much they improve one's vision when skiing on a cloudy day when it's really hard to see the moguls, etc.

This is also part of why proper fog lamps for your car are amber.  You don't want white or the evil bluish light for driving in rain, fog, snow, etc.  In fact, you don't want the bluish lights for any driving since they reduce one's ability to see details, and the shorter wavelength light is scattered more by the particles.  Instead, the old-school yellowish headlights are actually the best for our human eyes and to "penetrate" fog better.

The new LED lights in cars and trucks are awful.  It would be so easy for them to use the "warm white" LEDs, but bluish seems more "high tech" to people, so they probably sell more cars if the headlights are of that unfortunate bluish (high color temperature) variety.  It's all about marketing, I guess, not logic.

Off topic!  Ooops.  

smellyspice Posted at 1-1 20:54
LOL - thanks. Yeah, this is likely a rare circumstance - Snow stopped falling less than 24 hours before, it was solid overcast, so no shadows - AND - I wanted to try and fly down to the dock.

I wonder how long the mini would descend to land before it either gave up and turned off the motors and dropped to the ground. What would have happened if I let it continue to descend and just cancel it when it got "low enough" (based on my forward view on the camera. It was a long snowy walk to the dock, so I didn't want to find out! Any volunteers!?

I wonder how long the mini would descend to land before it either gave up and turned off the motors.
If it's like every other DJI drone (and I can't see why it would be), you could safely descend at full left stick down from any height.
Holding the left stick down should only shut down the motors when the drone is on the ground.

JeremyFr79 Posted at 1-1 19:51
It will only auto-land on full stick down once it detects (or thinks it detects) the "ground" at a set distance below, otherwise it'll just descend at "full throttle" never initiating auto land.

Exactly how I see it happening as well.  I feel like the distance where it goes from down mode to auto-land is about a half of a meter from what it thinks is ground.  Be it ground or your open palm.

This is how few drone flyers lost their drone!

If the VPS sensor measure height (correct or incorrect measuremnet) between zero and 0.5 meter AND full down stick is apllied for some moments >> an autolanding is commanded by the user, not intentionelly (like normal landing) but ....
If you don`t hear the landing audio than it will just land without know knowwing this. Only way to stop is this to stick 100% up! for short moment.
And did a test with my MM ; forward flying at 0.5 meters  and yes   it does go into an autolanding!

On DJI crafts where you can disable "landing protection" this problem is over when the option is disabled.  But on Spark and MM you cannot disable Landing Protection.

BTW DJI does not react to this, i did ask few times to change this habbit, i mean   forward flying with some speed and 100% down stick is almost never to have the intention to land a drone.  So change this and ask the user if he really wants to land, just a simple beep and question in the app.  Or just start a beep-beep * beep-beep * etc  to inform the user that he/she commanded a landing    DJI??

cheers
JJB

I had this same issue yesterday (after latest firmware update) - a confounding issue may be visibility, as a bank of moderately thick fog was rolling through while I was descending near full down stick with about 1/3 forward stick - drone was -2.3m altitude from home point but still about 65m above the ground and I wonder if the fog was interpreted as being close to the ground - controller announced "Landing, Landing, Landing" which I was able to abort on screen (although my cold fingers initially not recognized by my phone - will just up-stick if happens again).  

JodyB Posted at 2019-12-31 13:14
I'm not sure about what happened with your situation, and you may already know this, but the altitude is based off the take off point. So when you went below the take off point, that produced the negative value in altitude. Whether or not that has to do with what happened in your case, I'm not sure. I know I've taken off from a mountain side and decended to around -75 feet without issue, but that was prior to the .004 update. You might post your flight log so we can see if we can figure this out.

Hi there, i have a mini two and i am goin to set a home point at 1000 m a t.m, i am thinking of flyin 1000 meteres at 55 meteres and then i wad thinking on a descent of 800 m, birdes eye view onto a picnic tabke, tht would be 750 meters bellow mu homepoint, on a cliff edge,,! Is tht possibke, this is only goin to be my second flight, thank you if any one replys#

djiuser_J9KZbDiR5hcf Posted at 4-3 05:18
Hi there, i have a mini two and i am goin to set a home point at 1000 m a t.m, i am thinking of flyin 1000 meteres at 55 meteres and then i wad thinking on a descent of 800 m, birdes eye view onto a picnic tabke, tht would be 750 meters bellow mu homepoint, on a cliff edge,,! Is tht possibke, this is only goin to be my second flight, thank you if any one replys#

I also havnt been asked for a firmware update yet so i am very juvious right now, can the mini 2 fly below altidude of a set homepoimt at ease, there will be a mountain between me n it, the signal.is ovbiously gps# so is it ok to do this

djiuser_J9KZbDiR5hcf Posted at 4-3 05:18
Hi there, i have a mini two and i am goin to set a home point at 1000 m a t.m, i am thinking of flyin 1000 meteres at 55 meteres and then i wad thinking on a descent of 800 m, birdes eye view onto a picnic tabke, tht would be 750 meters bellow mu homepoint, on a cliff edge,,! Is tht possibke, this is only goin to be my second flight, thank you if any one replys#

Where in the UK would you be able to fly such a flight?  From the out set I have to say I think this would be a VERY UNWISE FLIGHT to make.
Reasons in order of increasing risk.
1) I'd be rather worried about wind anywhere that it is even possible.
2) Wind aside I would also have concerns about being able to get the drone back home, simply because the climb back will be with a fairly well discharged battery. I am assuming your are going to try to bring the drone back to you and not land on that picnic table.
3) AND THE REAL DANGER I also suspect this will be WELL beyond your visual range and or line of sight which is probably DANGEROUS as anywhere where such a flight is even possible may be an RAF and possibly USAF low-level training ground for fast jets as well as 4 engined transports.
I doubt that even in VLOS you'd have time to get out of the way of a fast jet.


Google "Mach loop" and even there I doubt you could make a 750m descent.
https://www.youtube.com/results?search_query=mach+loop



BE VERY CAREFUL BETTER YET DO NOT FLY THIS FLIGHT.

djiuser_J9KZbDiR5hcf Posted at 4-3 05:18
Hi there, i have a mini two and i am goin to set a home point at 1000 m a t.m, i am thinking of flyin 1000 meteres at 55 meteres and then i wad thinking on a descent of 800 m, birdes eye view onto a picnic tabke, tht would be 750 meters bellow mu homepoint, on a cliff edge,,! Is tht possibke, this is only goin to be my second flight, thank you if any one replys#

Is tht possible, this is only goin to be my second flight
Yes ... it could be possible.
But if it's only your second flight, you don't have enough experience to be getting so adventurous.
There are potential problems no-one can guess at from your sparse description and things you couldn't understand or imagine.
You have a lot to learn about all the things that can go wrong and how to make sure they don't.

Jeepers I didn't see the bit about it being their second flight.
That's even worse.

djiuser_J9KZbDiR5hcf Posted at 4-3 05:21
I also havnt been asked for a firmware update yet so i am very juvious right now, can the mini 2 fly below altidude of a set homepoimt at ease, there will be a mountain between me n it, the signal.is ovbiously gps# so is it ok to do this

I really think you should think twice about trying such a flight, and as others have said learn how to fly safely away from other people, I still get uneasy if my aircraft starts to look small. I think it's a disaster waiting to happen, fly safely.

djiuser_J9KZbDiR5hcf Posted at 4-3 05:21
I also havnt been asked for a firmware update yet so i am very juvious right now, can the mini 2 fly below altidude of a set homepoimt at ease, there will be a mountain between me n it, the signal.is ovbiously gps# so is it ok to do this

Don't even think about it.  It's a foolhardy plan.

djiuser_J9KZbDiR5hcf Posted at 4-3 05:21
I also havnt been asked for a firmware update yet so i am very juvious right now, can the mini 2 fly below altidude of a set homepoimt at ease, there will be a mountain between me n it, the signal.is ovbiously gps# so is it ok to do this

Just to make perfectly sure:
You said there will be a mountain between you (the pilot) and the drone?
If so, in which particular situation will that mountain break your direct line of sight to the drone?

djiuser_J9KZbDiR5hcf Posted at 4-3 05:21
I also havnt been asked for a firmware update yet so i am very juvious right now, can the mini 2 fly below altidude of a set homepoimt at ease, there will be a mountain between me n it, the signal.is ovbiously gps# so is it ok to do this

To be fair, i dont think i can follow the 1st of your posts 100%.

From what i can understand, the flight is technically possible but also illegal due to the distance, 1) its a max of 500m distance allowed and 2) VLOS is lost, it would be irresponsible of me if i didnt mention that but also hypocritical and that's all i will say there.

I can't pretend to know where you're referring to as the flight location but there are a few points to note;

• as already mentioned, low flying fast jets could be a concern although they are limited to certain areas of the UK, the Mach loop being 1 (central Wales), Northern Scotland another and England/Scotland border. the low flights are normally between 500 and 1000ft agl. the do publish a timetable on the .gov site, 1 point to mention though is that if its anything like here, they dont fly at the weekends or on bank holidays
• life flights are a major concern too, probably more so with it being mountainous, helicopters do not follow the ground separation rules like planes do.
• another concern is the mountain between you and the drone, you will lose connection if the mountain breaks line of sight with the drone and the drone will start RTH
• download UAV Forecast, this will give you the winds at different altitudes up to 1500m
  

It happen to me too with the mini 3 pro after updating the software, it dose not allow me to fly below 0 high point and enter to automatic landing, even if I tried to do it very slowly it just dose not work at all...

djiuser_6ECr5zZPnGrl Posted at 10-5 02:11
It happen to me too with the mini 3 pro after updating the software, it dose not allow me to fly below 0 high point and enter to automatic landing, even if I tried to do it very slowly it just dose not work at all...

Hi,

Best to get advice/help is to upload your flightlog for this issue.

Use this > https://www.phantomhelp.com/LogViewer/Upload/
Post the uploaded link on here

cheers
JJB