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When does Return to Home altitude fail?
1821 11 2021-1-12
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mister_davo
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I set my Return To Home Altitude to 150 feet
I am flying the Mini 2 at 100 feet AGL
Return to Home is initiated.
    - Mini 2 rises 150 feet, then returns to GPS Home coordinates. Perfect!
or
I am flying the Mini 2 at 350 feet AGL
Return to Home is initiated.
    - Mini 2 doesn't rise at all and simply returns to GPS Home Coordinates. FAil.

Why does the starting altitude affect whether the Mini uses the RTH altitude setting?
Sometimes I'm flying even at 800 feet AGL when I've been climbing over a hill for example and I might literally only be 10 feet over the actual ground, but if the RTH kicks in and it seems it would cause the Mini to rise more than 400 feet higher than the STARTING altitude, it simply will not rise first. This seems a REALLY bad idea. Already cost me my first Mini 1 - smashed into side of cliff as a result.

Am I doing something wrong?


Davo
2021-1-12
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Lisa3 AKA Karen
Second Officer
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I could be missing something but I don’t see an issue.
If it’s below the set RTH it will rise to the RTH altitude and return.
If it is flying above the RTH setting it will return at it’s present altitude.
All bets are are off, I believe, if it’s within 50 meters of the home point, then it will return at its current altitude.

Your starting AGL is 0 no matter what your elevation might be.
It does not compensate for actual elevation above sea level.

If you power up your drone at the base of a hill, set your RTH to 300' fly up and over said 800' hill then down the other side and enable RTH,  it will not end well.

I will be corrected if mistaken but I believe that is the way it works (not like in The Shining corrected).

2021-1-12
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GaryDoug
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It is up to the operator to determine what RTH altitude is needed for the location. If there is a hill that is 350 feet high and the drone may need return above that, then set the RTH to 400 ft. Use something like a MA2 if you want better obstacle avoidance during RTH.
But if you mean the altitude of the home point, it should reference that level to zero at launch already.
2021-1-12
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JohnLietzke
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The drone does not descend to the RTH Height it will only elevate.  Best to ensure you have clearance of any objects in the RTH path, so set the RTH Height higher than anything in the area when possible.  Be mindful of altitude restriction.
2021-1-12
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Donut
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JohnLietzke Posted at 1-12 15:52
The drone does not descend to the RTH Height it will only elevate.  Best to ensure you have clearance of any objects in the RTH path, so set the RTH Height higher than anything in the area when possible.  Be mindful of altitude restriction.

Two things.
If you are not more than 150 feet from home it will go down where it is at.
The 150 RTH is where you are standing so if it is up a hill 800 feet it is going  straight down to 150 feet above where you are standing. Which means it will go down 650 feet where it is at when you initiate RTH.
I watched a guy do that when he was flying the side of a mountain.
So wherever it’s at you need 150 be able to make sure it can go straight down to the RTH height.
2021-1-12
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JohnLietzke
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I think I understand what you are saying.  

The HomePoint is a fixed location based on GPS and not the location of the Remote Control is at.

If the drone is within 5-50m (150ft) of the Home Point then it will not change height but simply change direction and return to the Home Point at the current height it was at when the RTH was initiated.   

A practical example, the drone is 75ft away and at height of 50ft.  If you were to initiate an RTH it would stay at 50ft in the air and fly the 75ft to the Home Point then descend to 0ft and land.  But, if you were standing on the ground flying up to the top of a tall building.  The drone is 75ft away and at a hight of 800ft.  When an RTH is initiated the drone will fly at a height of 800ft back to the HomePoint.  Once over the HomePoint it will descend and land.

If the HomePoint is 1,000ft from the previously mentioned building and the drone is flying at 800ft, then it will depend on what the RTH Hight is set at in the DJI Fly app.  If the RTH Height in the DJI Fly app set is to 900ft then the drone will ascend (100ft) to that height and fly at 900ft to the HomePoint and land.  If the RTH Height is set at 400ft the drone will maintain the 800ft height as it flies back to the HomePoint then land.  

If the drone went down below a cliff you were standing on 100ft it would detect that the hight is -100ft and would ascend to the RTH Height set in the DJI Fly app.  So if the RTH Height was set in the DJI Fly app to 400ft the drone would ascend 500ft before flying back to the HomePoint and landing.  According to DJI's phone support if the drones height is below the height of the Home Point it will always ascend to the RTH Height set in the DJI Fly app before flying to the HomePoint and landing.  Support said this may also happen if the drones is less than 2 meters in height from the HomePoint.




2021-1-12
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Labroides
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Why does the starting altitude affect whether the Mini uses the RTH altitude setting?
It doesn't

Am I doing something wrong?
Yes .. not realising that RTH height, like all heights is relative to Home = zero
Re-read the RTH section of your manual, it's important and quite detailed.
2021-1-12
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Donut
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Wonder if it could be possible for dJI To add in the safety section  that would give us the option to return to home at its present height if it’s height is above the RTH height. Then there would not go down to RTH first before returning. And that way it would descend down into the ground..
I may be wrong but it’s just a thought.
Doug
2021-1-12
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JJB*
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Donut Posted at 1-12 19:00
Wonder if it could be possible for dJI To add in the safety section  that would give us the option to return to home at its present height if it’s height is above the RTH height. Then there would not go down to RTH first before returning. And that way it would descend down into the ground..
I may be wrong but it’s just a thought.
Doug

Hi Doug,

Flying above the RTH height setting and RTH engages ; it will never descend.

cheers
JB
2021-1-13
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GaryDoug
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^^^^ Right. The only exception to that is with the Power Saving Return to Home option like in the MA2. But even that is a gradual descent.
2021-1-13
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djiuser_uvIzjtdw8jDc
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JohnLietzke Posted at 1-12 18:09
I think I understand what you are saying.  

The HomePoint is a fixed location based on GPS and not the location of the Remote Control is at.

[I]If the drone went down below a cliff you were standing on 100ft it would detect that the hight is -100ft and would ascend to the RTH Height set in the DJI Fly app.  So if the RTH Height was set in the DJI Fly app to 400ft the drone would ascend 500ft before flying back to the HomePoint and landing.  According to DJI's phone support if the drones height is below the height of the Home Point it will always ascend to the RTH Height set in the DJI Fly app before flying to the HomePoint and landing.  Support said this may also happen if the drones is less than 2 meters in height from the HomePoint.[/I]

This is what I came looking for.

Thanks

2021-11-27
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JohnLietzke
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djiuser_uvIzjtdw8jDc Posted at 11-27 15:40
If the drone went down below a cliff you were standing on 100ft it would detect that the hight is -100ft and would ascend to the RTH Height set in the DJI Fly app.  So if the RTH Height was set in the DJI Fly app to 400ft the drone would ascend 500ft before flying back to the HomePoint and landing.  According to DJI's phone support if the drones height is below the height of the Home Point it will always ascend to the RTH Height set in the DJI Fly app before flying to the HomePoint and landing.  Support said this may also happen if the drones is less than 2 meters in height from the HomePoint.

This is what I came looking for.

This nuance was resolved in an update many months ago from my understanding.  But I have not tested it again.

The incident stands out to me.  But the issue was that once I descended close to the home points elevation within 500ft the Mavic Air 2 attempted an auto landing.  

Fortunately, I had enough time to cancel it. It was a very close to being swallowed by the ocean.  Probably less than 10 ft.
2021-11-28
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