I had an interesting experience this weekend when flying on a mountain. I was on a mountain with switchbacks. Switchbacks for those that may not know the term, is basically when you drive up a hill and encounter a type of U-turn to keep going up the mountain.
I was standing on a switchback, I flew the craft out to the switchback below me, and attempted to lower the craft to get closer to the ground. The craft then signaled, ok, I'm landing! Whoa. What apparently happened is, the craft was looking at the altitude where I took off and saying, you are going negative. That doesn't really make sense though. It has a bottom sensor so it knows if I'm close to the ground. Is this known behavior? I won't be in this scenario hardly ever but I would like to understand what happened.

What apparently happened is, the craft was looking at the altitude where I took off and saying, you are going negative.
Flying lower than your launch point makes no difference to your drone and definitely does not cause the drone to land.
Could you imagine anyone programming a drone that way?

I would like to understand what happened.
I would too but you didn't explain what happened well enough to tell much.
But f you post recorded flight data from the flight, it willprobably be obvious.

Sounds more like it sensed the land below it,   you could try looking at the log - http://phantomhelp.com/logviewer/upload/

Negative altitude readings do not cause the drone to land - I've done it many times. What may have caused the drone to attempt to land is if the VPS sensed the ground as you were continuing to descend or the drones altitude ASL was too high or a malfunction of some description with the drone. Best post the log file for a more precise evaluation.

I've never had a situation like that. I frequently take the drone to hilltops and fly below the altitude of the take-off point without incident.

OK. Thanks for the responses. I will see if I can pull a log. I would hazard a guess that when it happened I was about 3,000 feet above sea level. I was at cloud level so it was pretty misty. It's possible the mist confused the sensor as the ground. The cloud tops were at around 4,000 feet and I had no other issues during any of the flying, all the way up past the 5,000 foot level.

For reference, I've linked the video to the spot where the incident occurred. I was trying to lower the craft to that road below. Maybe the visual gives additional hints until I can find the log etc.  
Well, it seems like it didn't like the YouTube time stamp. Forward to 1:24.

PS. If you're watching the video, you might say, well you were flying on the hill. It sensed that. This is the final edit. When I was trying to descend, I was further out on the road (I'm fairly sure). Hmmm. I wonder if I have raw footage of that. Now it has me wondering if I wasn't as far out as I thought.

Hiya,

Guessing is never a good idea....but your drone saw 0.5 meter VPS height while 100% down stick was applied = drone into autolanding mode.

But flightlog will probably explain what happend, so forget my guessing   ;-)

cheers
JJB

To answer your question Labroides, I was trying to descend down to this road as I knew my friends would be coming up it shortly. And no, it doesn't make sense that it would be programmed that way which is why I wanted clarification that something else was the cause, be it craft, operator or ?

Here is the log in question. https://www.phantomhelp.com/logviewer/R1VUOU3FMDPKNKO689CY   I had 2 incidents. The first one at 2:20. That's not the one I referenced above but it startled me non the less. The map seems just ever so slightly off. I recall that I was slightly north of the location, more towards the road. You can see I was 21 feet up so why it said I'm landing was shocking.

The one that I referenced above is at 3:39. As you can see, I seemed clear of the hill you see above and over the road. That being said, if the map is just slightly askew, maybe I was just close enough to the hill that it saw it. I was recorded at 16 feet though and I was literally looking straight out at it so it would have had a good 30 plus feet to the road. My experience so far in the first month is, auto landing only takes place when you are maybe 6 feet above the ground. I certainly had more than that.

Thanks for your assistance with this. I'm very curious to understand what happened.

InsaneDiego Posted at 10-26 07:08
Here is the log in question. https://www.phantomhelp.com/logviewer/R1VUOU3FMDPKNKO689CY   I had 2 incidents. The first one at 2:20. That's not the one I referenced above but it startled me non the less. The map seems just ever so slightly off. I recall that I was slightly north of the location, more towards the road. You can see I was 21 feet up so why it said I'm landing was shocking.

The one that I referenced above is at 3:39. As you can see, I seemed clear of the hill you see above and over the road. That being said, if the map is just slightly askew, maybe I was just close enough to the hill that it saw it. I was recorded at 16 feet though and I was literally looking straight out at it so it would have had a good 30 plus feet to the road. My experience so far in the first month is, auto landing only takes place when you are maybe 6 feet above the ground. I certainly had more than that.

Hi,

Ssee your data in my chart.

VPS height measured 0.6-0.5 meter with 100% down stick = a command to perform a forcelanding.
If VPS did measure correct or incorrect this distance, cannot see that from my pc....  ;-)  
But checking the VPS values for longer period, guess it was accurate.

Default Autoland height is at 0.5 - 0.6  meters, so this times 3 for feet. So it is not 6 feet.You can check this your self,  hover at 100 feet, 100% down stick and keep 100% down stick all the time ; see the rate of descend slows down when VPS is getting within range, drone stops at 0.5 [1.6-1.7 feet] meter above ground (while still 100% down stick, shortly after it will ter landing mode)



cheers
JJB

Thank you JJB. Now, English please.    I'm going to attach two snapshots. Now that I have the log, I was actually recording at the time. These images represent the moment it decided to auto land. In both cases, and specifically the 3:39 one we're talking about, I'm nowhere near the ground. If I understand your lingo, you're saying the Vision System thought I was within 3 feet of the ground?

This is the 2:20 incident.


This is the 3:39 incident

Hi,

Oke, if you are right about where you were flying that time (ofcourse you are right being there in control) than the VPS height sensor was incorrect measuring.
But for the software its the same,  so when 'measuring' 0.5 AND 100% down stick = enter forcelanding.
Must be the fog on the sensor.

But your reaction was oke, just pull up and this will cancel the forcelanding.

happy many landings,
cheersJJB

JJB* Posted at 10-26 08:13
Hi,

Oke, if you are right about where you were flying that time (ofcourse you are right being there in control) than the VPS height sensor was incorrect measuring.

Perfect. Yes, I would definitely attribute the confusion on the fog in this case. I live in Southern California and we don't get much bad weather so it was the first time flying in these conditions, let alone on a mountain! Thankfully I was wearing my glasses so I could read the screen. I had done enough practice that I didn't panic too badly. Thank you for the analysis. It was exactly what I needed.

InsaneDiego Posted at 10-26 08:27
Perfect. Yes, I would definitely attribute the confusion on the fog in this case. I live in Southern California and we don't get much bad weather so it was the first time flying in these conditions, let alone on a mountain! Thankfully I was wearing my glasses so I could read the screen. I had done enough practice that I didn't panic too badly. Thank you for the analysis. It was exactly what I needed.

my pleasure, didn`t you heard the audio warning?  i sometimes forget to set the mobile device volume at 100%, with traffic noise around me

Problem with this unwanted force landing is that even when flying with some forward speed it still enters into such a landing. And who wants to land its craft flying with forward speed ??

But unfortunetly DJI will not react on this....

cheers
JJB

JJB* Posted at 10-26 10:25
my pleasure, didn`t you heard the audio warning?  i sometimes forget to set the mobile device volume at 100%, with traffic noise around me

Problem with this unwanted force landing is that even when flying with some forward speed it still enters into such a landing. And who wants to land its craft flying with forward speed ??

I did hear the audio warning. If I'm not wearing my glasses though, reading the screen could be a challenge depending on what it said.

Hello InsaneDiego, thank you for reaching us out. I appreciate your inquiry about the Mavic Air 2 that is not allowing you to descend closer to the subject. Watching your video posted as well as the photos shows that the place where you are with was quite misty. As the Mavic Air 2 has limitations in-terms of its Vision System it will affect the accuracy. You can check the information below for additional information about the Mavic Air 2 vision system.

That can be found under the Mavic Air 2 manual at page 17.
https://dl.djicdn.com/downloads/ ... Manual_v1.2_en_.pdf

I hope you find this information helpful. Fly safe! Thank you for your support.

Ok you're killin me ova here............I used to ride motorcycles up and down Palomar on Sundays......till the clowns with slicks and full blown racebikes showed up.

I fly at SEFSD.org in Mission bay.....and jobs when I can......I'm on FB as Randy Wynant.   Drop in.....

Randy

Sounds like you lacked adequate satellite locks and the GPS position was not being updated properly.  I have done something similar with an AIR 2 taking off before the Home Point was set and another time the GPS was just off on the map and I landed and waited about 30 seconds and that resolved the problem.  

rwynant V1 Posted at 11-1 15:24
Ok you're killin me ova here............I used to ride motorcycles up and down Palomar on Sundays......till the clowns with slicks and full blown racebikes showed up.

I fly at SEFSD.org in Mission bay.....and jobs when I can......I'm on FB as Randy Wynant.   Drop in.....

Hi Randy,

I know what you mean. You know there is a lot of bicycle traffic up that mountain and the side of the road is about 18". Somewhere near the top, up comes a band of racing corvettes and stuff like that. Loud as heck, doing way above the speed limit. It was unreal. Up near the top is nothing but a set of switchbacks and you can't see what is around the corner. Way too macho.

JohnLietzke Posted at 11-1 15:31
Sounds like you lacked adequate satellite locks and the GPS position was not being updated properly.  I have done something similar with an AIR 2 taking off before the Home Point was set and another time the GPS was just off on the map and I landed and waited about 30 seconds and that resolved the problem.

Thanks for the response John. I completely understand what you are saying and I never leave my position until I get the RTH point set, which also means enough satellite locks.

That wasn't the case here though. I think I had 13-18 satellites as confirmed by the log. The cloud layer I was in seemed to cause the situation and if I'm flying in fog or clouds, I'll definitely know that it can be dicey and cause some undesirable behavior. I didn't realize that the Vision System could actually take control as it did. I had the craft right in front of me so I thought it would be much like Sport mode where you're on your own. An education and thankfully no bad results this time out.