Flying lower than launch height - Possible?

[Izzikiorage]

A weird question. Does the air 2s or any other DJI drone restrict it from flying below the height at which it was launched

The case - launched the drone from a rooftop and was trying to fly between the buildings. The drone would go down till the rooftop level (zero height in the controller) and then not go any lower.

Was flying in P and cine mainly but did try sport mode and that did not help. Has anyone tried this, will it go to negative height in the controller?

 

[Yorkshire_Pud]

Below take off should be possible, there is a -248ft log in the thread

DJI mini fell off on Cliff of Moher Ireland. Any idea how to lift it up?

Fishing pole with large treble hook? I think that's possible. However, the "fishing" person need to sit on the cliff edge. That's dangerous.

mavicpilots.com

Though I do have a vague recollection of some people reporting problems.
Post the flight log, there might be an answer in that.

 

[Izzikiorage]

I assume you mean the flight log in the DJI Air app. Read around a bit and have attached the file

Even while pushing the sticks down It kept a min height of 0.1m. Finally got to a - 2.8m when landing (guess the initial height of launch recorded was wrong)

 

[Meta4]

A weird question. Does the air 2s or any other DJI drone restrict it from flying below the height at which it was launched

The case - launched the drone from a rooftop and was trying to fly between the buildings. The drone would go down till the rooftop level (zero height in the controller) and then not go any lower.

Whether you fly above or below the launch point makes no difference to the drone. makes no difference to the drone

Even while pushing the sticks down It kept a min height of 0.1m. Finally got to a - 2.8m when landing (

The time you thought it wasn't descending the VPS sensors were detecting something close below it.
Landing protection stops the drone descending further unless you keep the left stick down for two full seconds after landing protection initiates (and you didn't do that).

Your drone would have easily descended below launch height if there wasn't something close below the drone.

guess the initial height of launch recorded was wrong)

The initial height is always reset to zero when you power up, as yours was in this flight.
It is common to see the indicated height on screen drift 2-6 metres over the duration of a flight.
That's what you observed.

 

[Izzikiorage]

Thank you so much, I'm guessing it was the fog getting picked by the sensors. Will try this again on a clearer day

 

[Yorkshire_Pud]

Thank you so much, I'm guessing it was the fog getting picked by the sensors. Will try this again on a clearer day

Be careful of flying in fog, the interaction between fog and the VPS can cause problems, e.g.
a) very slow descent rates, when the drone thinks it it close to landing on something, something being the fog itself
b) fooling the drone into initiating "landing" behaviour when you don't want it to.

It can also restrict your ability to see the drone and the airspace around the drone.


The log on phantomhelp = DJI Flight Log Viewer - PhantomHelp.com

 

[Izzikiorage]

Yup, experiment for clear days then

Also the logs are amazing, how do i read this and how did you figure out that at some point the downward sensors did not allow me to go lower? I'm more worried about the drone starting an auto landing sequence due to fog

 

[Yorkshire_Pud]

Yup, experiment for clear days then

Also the logs are amazing, how do i read this and how did you figure out that at some point the downward sensors did not allow me to go lower? I'm more worried about the drone starting an auto landing sequence due to fog

Download the csv from pantomhelp and open it as a spread sheet.
Alternatively download CsvView.

CsvView Downloads

(windows only) instal it and use it to process that csv, then work your way through the drop down menus.

 

[Yorkshire_Pud]

I'm more worried about the drone starting an auto landing sequence due to fog

Yep, I believe you have to force that, by holding the throttle closed as Meta4 mentions and I suspect you could cancel it by giving full throttle.
That said I think the bigger danger is the slow descent, especially if you fly the drone to low battery levels and are high, which you did not do, and then the risk is the battery will die and the drone's motors stop.

 

[hagman23]

A weird question. Does the air 2s or any other DJI drone restrict it from flying below the height at which it was launched

The case - launched the drone from a rooftop and was trying to fly between the buildings. The drone would go down till the rooftop level (zero height in the controller) and then not go any lower.

Was flying in P and cine mainly but did try sport mode and that did not help. Has anyone tried this, will it go to negative height in the controller?

I do it all the time. Living in the mountains, I take off from high elevations and fly below my takeoff height with no issues in every mode of flight.

 

[RangerEd]

I do it all the time. Living in the mountains, I take off from high elevations and fly below my takeoff height with no issues in every mode of flight.

I do it all the time too. I fly at the beach and in some places I'm 100-200' above the waterline.

 

[Parkerjh]

no issues at all - I fly into quarries and ravines 100's of feet below takeoff

 

[Yaros]

Does the air 2s or any other DJI drone restrict it from flying below the height at which it was launched

Yes, done that probably a hundred times with the Air 2 and Air 2S, no issues. The only downside is that the height in the fly app is reported as negative relative to home point, so don't rely on it.

Other than that it's good to fly!
If you're wondering what will happen in an RTH/Loss of signal situation, here is a video on it (not mine):

 

[Parkerjh]

@Yaros I'm curious, what do you mean, "don't rely on it". Why not? I rely on it equally whether it's a positive or negative number.

 

[Yaros]

Why not?

The reason I said that is because the altitude will be not relative to ground, it will be relative to the homepoint altitude, takeoff location.

 

[Parkerjh]

The reason I said that is because the altitude will be not relative to ground, it will be relative to the homepoint altitude, takeoff location.

It works the same way for positive altitudes

 

[Xitor]

Good thing there is no artificial floor at 0 feet because frequently when flying for a long time the barometric pressure will change enough for the take off point to now register a negative number list -11. I'd hate for the drone to stuck 10 feet off the ground.

 

[Izzikiorage]

So got a chance to try this today and still some issues. Maybe its a setting that I've messed up

Started flying on top of a small hill. Had it active track a car that i was travelling in. When we stopped at the base, i updated the home point to controller location. When i tried to land it reached zero altitude (basis the orignal launch height i think) and just would not come down. Pushing the stick down activated landing mode some 20m in the air (there were no obstacles below it) and it very slowly landed after 5-10 min.

Any idea where I'm going wrong. As per the responses above it should just allow me to fly under the launch height

 

[Meta4]

So got a chance to try this today and still some issues. Maybe its a setting that I've messed up

Started flying on top of a small hill. Had it active track a car that i was travelling in. When we stopped at the base, i updated the home point to controller location. When i tried to land it reached zero altitude (basis the orignal launch height i think) and just would not come down. Pushing the stick down activated landing mode some 20m in the air (there were no obstacles below it) and it very slowly landed after 5-10 min.

Any idea where I'm going wrong. As per the responses above it should just allow me to fly under the launch height

Your drone does not care whether you fly higher or lower than the launch point.
The drone doesn't care how much higher or lower you want to land relative to the launch point.
It's all irrelevant.
Try without complicating things with auto-tracking.

 

[Izzikiorage]

Had switched off auto tracking and all by the time i started landing. The only extra step was updating the home point to the controller location. But still it started an auto land sequence pretty high up