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Negative altitude?
1730 10 2021-5-15
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AlanGNW
lvl.1
Flight distance : 40256 ft
Spain
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Forgive the newbie question. I have yet to fly the Air 2 I bought recently. Here's the question. I live in a fairly mountainous region and I am likely to fly from high points into valleys.

Given this, if the drone is below the height at which it took of, does it realize it's below the RTH height? Will it...

A) Read the ground below to establish the RTH height
B) Will it take the RTH height after reaching the altutude at the height from which it took off

Thanks.
2021-5-15
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Geebax
First Officer
Australia
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The aircraft cannot 'read' the ground as you suggest, it has no method of doing so. The altitude is measured using a barometer, and is set to zero when you take off, so if you fly down into a valley, it will display a negative reading. If you fly upwards, it will display the altitude above your launch point. Yes, it knows it is below the RTH height you set, so if you had set the RTH height to 100 feet, during return-to-home it will climb to 100 feet above your launch point to come home.



2021-5-15
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Labroides
Core User of DJI
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Australia
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A) Read the ground below to establish the RTH height
Unless you get within the very limited range of the VPS sensors, your drone has no way to "read the ground".
You could send it 1000 feet down into the grand canyon and it wouldn't know if it was 50 feet or 5000 feet above the bottom.

B) Will it take the RTH height after reaching the altitude form the height from which it took off.

It doesn't matter if the drone's altitude is + or negative.
Like all other heights, the RTH height is relative to where the drone was launched.
2021-5-15
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AlanGNW
lvl.1
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Spain
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Thank you both....
2021-5-15
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djiuser_YyDMf0V8bjrf
lvl.2
Flight distance : 359619 ft
United States
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-------> HELP# <-------
   Hi, Good morning!  I always fly over the bay waters. The only area that is clear of tall buildings where I live.

  Is there a way to set a " LOW ALTITUDE WARNING" on the Mavic air 2 or any other Mavic drone?

  I get very distracted and lost altitude moving the left joystick, not trying to lower the altitude but rotating it. Sometimes I forget to look at the altitude for a long time.

  A "LOW ALTITUDE (pull up! ) or Terrain  WARNING" would be life-saving:

The idea is to increase altitude if I get below 5 or 10 meters without realizing I did. To prevent getting submerged in the water.  I can't believe there are so many warnings except a low-altitude one. All commercial airplanes have several "LOW TERRAIN WARNINGS" at different altitudes.

Could you please; contact DJI engineers and bring the idea? I am still a novice, and I am even learning to speak English. I dont know how to do it by myself.

The warning will bring more safety and joy to the flying experience and would be a very substantial safety improvement for everybody.

  Sincerely, Lesmex F
2021-6-8
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Labroides
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Is there a way to set a " LOW ALTITUDE WARNING" on the Mavic air 2 or any other Mavic drone?
No

I get very distracted and lost altitude moving the left joystick, not trying to lower the altitude but rotating it. Sometimes I forget to look at the altitude for a long time.
Just like driving a car or flying a plane, you need to pay attention to what's going on.


All commercial airplanes have several "LOW TERRAIN WARNINGS" at different altitudes.
And those planes cost how much more than your drone?

2021-6-8
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djiuser_YyDMf0V8bjrf
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Flight distance : 359619 ft
United States
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Labroides Posted at 6-8 15:46
Is there a way to set a " LOW ALTITUDE WARNING" on the Mavic air 2 or any other Mavic drone?
No

Hi!
A low terrain warning won't cost anything. The technology is already on the drone. If it detects altitude, it can send a warning when it's below, let's say, 5m.
2021-6-9
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Frank Alonso
lvl.4
Flight distance : 785049 ft
United States
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One thing to keep in mind when launching your Mini 2 is the height you launched it from.  I took my Mini 2 out for a few laps around the park behind my house.  I thought it would be good practice to fly up and then under the canopy of a nearby cluster of trees.  I did not realize that I launched from my porch is 6 feet above the ground.   Thinking my altitude was from the ground level I nearly crashed into the trees.  
2021-6-9
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Labroides
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djiuser_YyDMf0V8bjrf Posted at 6-9 12:15
Hi!
A low terrain warning won't cost anything. The technology is already on the drone. If it detects altitude, it can send a warning when it's below, let's say, 5m.

I guess it's too much to expect new flyers to be aware of where their drone is and its surroundings.
DJI should make their drones do everything for them.
2021-6-9
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lesmex
lvl.2
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United States
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Labroides Posted at 6-9 15:19
I guess it's too much to expect new flyers to be aware of where their drone is and its surroundings.
DJI should make their drones do everything for them.

Bitter soul, I dont need you to tell me what I have to do if it's not a constructive idea.

I am not expecting anything. It was my comment and personal opinion. Yes, it's an excellent idea so the drone pilots can focus more on recording videos and having fun without worrying about crashing.

All the DJI drones have the altitude measured at all times. It will probably take less than two programing lines: to create the low terrain warning.  Altitude < 5m: warning.

When you try to be mean, you just let everybody know how sad and miserable your life is.





2021-6-9
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JJB*
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lesmex Posted at 6-9 16:22
Bitter soul, I dont need you to tell me what I have to do if it's not a constructive idea.

I am not expecting anything. It was my comment and personal opinion. Yes, it's an excellent idea so the drone pilots can focus more on recording videos and having fun without worrying about crashing.

Hi,

If only DJI would show the VPS height (bottom sensor) in the FlyApp ! as in the GO 4 app where this height is seen. (and mayby colour the height red below user defined threshold value)

Life can be so simple....

Many happy landings,
cheers
JJB
2021-6-9
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