What's the results of descending below the takeoff altitude?

[RkyMtnHigh]

I've searched the threads and seems like there's a difference of opinion. I'm travelling to Moab, Utah in June for an extended weekend of exploring many of the trails out there. As many of you may know the scenery is spectacular and I'm excited to get some great footage. With that said, my question is this, since there are many desert canyons there, if I descend into one and go down say 50-100ft below the recorded takeoff altitude, how can I expect, if anything, for the drone to respond? I'll be flying a Mavic Air1.

 

[THE CYBORG]

Same as normal

 

[old man mavic]

@RkyMtnHigh ,just remember that in the event of a RTH that the drone will have quite a climb back to the top so factor that in to your RTH set height and remaining battery charge to allow for that

 

[Gringorio]

Also consider GPS signal strength if you descend into narrow and/or deep canyons.

 

[Thomas B]

The altitude should show a negative number once you descend below TO point.

 

[slup]

2 obvious thing's & maybe one unexpected ...

1. The height display will go negative in the app if you descend below the HP.

2. You risk violating max height above ground if triggering the failsafe RTH, this if going enough below HP & have a set RTH height high above the HP ... this as the AC will ascend up before moving to higher ground ... i.e. height from ground in canyon up to HP + RTH height from the HP might go over 400ft.

3. The surprising one ... if going far below the HP in a canyon that will increase the risk for a weak GPS reception. Then you might not be able to ascend up to the HP anymore ... all according to the height limitations in the user manual.

 

[RkyMtnHigh]

@RkyMtnHigh ,just remember that in the event of a RTH that the drone will have quite a climb back to the top so factor that in to your RTH set height and remaining battery charge to allow for that

I was going to figure that altitude difference into the RTH altitude. I was curious to know if the drone would sense that it's 50ft below takeoff altitude and automatically initiate RTH or attempt to auto-land, or if it would even do anything at all other than what I tell it to do?

 

[slup]

...I was curious to know if the drone would sense that it's 50ft below takeoff altitude and automatically initiate RTH or attempt to auto-land, or if it would even do anything at all other than what I tell it to do?

If you loose the connection down there, it will carry out a failsafe according to how you've set it up ... either RTH, hover or land. If you have set it to RTH it will behave according to the manual ... it will not deduct the negative height from the set RTH height, all heights is relative the HP. So if the set RTH height is 50ft & you descend 50ft down in a canyon it will ascend in total 100ft.

But please note point 3. in post #6 ... that one really can surprise you.

 

[okw]

3. The surprising one ... if going far below the HP in a canyon that will increase the risk for a weak GPS reception. Then you might not be able to ascend up to the HP anymore ... all according to the height limitations in the user manual.

I wouldn't think this would be an issue, since the Mavic will be well below the 16 or 98 feet limitation.

EDIT: Assuming these height limitations are above take-off point.

 

[slup]

I wouldn't think this would be an issue, since the Mavic will be well below the 16 or 98 feet limitation.

It will be a real issue, it's been a couple cases of that here at the forum ... when you loose the GPS the zero HP height will be lost & the height limit counts from where the drone is ... so if you descend enough down into a canyon & losing the GPS you might not be able to come back up to HP.

 

[Meta4]

I was going to figure that altitude difference into the RTH altitude.

There's no figuring necessary.
All heights are relative to the home point, whether they are negative or positive

I was curious to know if the drone would sense that it's 50ft below takeoff altitude and automatically initiate RTH or attempt to auto-land, or if it would even do anything at all other than what I tell it to do?

Your drone "knows" it's altitude relative to the home point at all times.
The earth is not flat all over and it's common for people to fly and descend from high points.
There's nothing different about it at all.

 

[Meta4]

I wouldn't think this would be an issue, since the Mavic will be well below the 16 or 98 feet limitation.

EDIT: Assuming these height limitations are above take-off point.

It's only an issue in a location where the drone loses GPS - like a narrow slot canyon.
If the drone has a clear view of much of teh sky, it will have good GPS reception and this won't be an issue.

But in the rare cases when it is an issue, the problem happens when the drone gets close enough to the ground for the VPS sensors can measure a distance to the ground.
Then due to poor programming, the drone will use the VPS altitude rather than the barometric altitude which is based on the home point.

This is a rare situation, you'll probably never encounter.

 

[RkyMtnHigh]

There's no figuring necessary.
All heights are relative to the home point, whether they are negative or positive

Your drone "knows" it's altitude relative to the home point at all times.
The earth is not flat all over and it's common for people to fly and descend from high points.
There's nothing different about it at all.

That's good to know. Thanks!

 

[RkyMtnHigh]

It's only an issue in a location where the drone loses GPS - like a narrow slot canyon.
If the drone has a clear view of much of teh sky, it will have good GPS reception and this won't be an issue.

But in the rare cases when it is an issue, the problem happens when the drone gets close enough to the ground for the VPS sensors can measure a distance to the ground.
Then due to poor programming, the drone will use the VPS altitude rather than the barometric altitude which is based on the home point.

This is a rare situation, you'll probably never encounter.

Really not planning on flying into any slot canyons, more like the large Grand Canyon type of canyons...very wide and open to the sky. I may not even fly down at all but was just wondering if I happen to come on a shot that would be pretty cool coming up over the ledge.

 

[Thomas B]

Really not planning on flying into any slot canyons, more like the large Grand Canyon type of canyons...very wide and open to the sky. I may not even fly down at all but was just wondering if I happen to come on a shot that would be pretty cool coming up over the ledge.

Just watch the satellite count and you can get some good shots.

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[cgmaxed]

I've searched the threads and seems like there's a difference of opinion. I'm travelling to Moab, Utah in June for an extended weekend of exploring many of the trails out there. As many of you may know the scenery is spectacular and I'm excited to get some great footage. With that said, my question is this, since there are many desert canyons there, if I descend into one and go down say 50-100ft below the recorded takeoff altitude, how can I expect, if anything, for the drone to respond? I'll be flying a Mavic Air1.

I have a Mav Air 2. I don't have a MAV air 1. On the Mav air 2 l just see a negative altitude read out. No changes occur otherwise. I fly off a 5 story building every day. Then I fly below my starting point. Nothing changes except the altitude indicator is negative. That's all. Maybe the Mav Air 1 isn't getting firmware updates to eliminate this limitation? I don't know. I guess, do what the other pilots do, turning off downward sensors. Good Luck.

 

[Meta4]

Maybe the Mav Air 1 isn't getting firmware updates to eliminate this limitation? I don't know. I guess, do what the other pilots do, turning off downward sensors. Good Luck.

All DJI drones behave the same way when they fly below the launch point.

 

[STS-Mavic-Mini]

I've searched the threads and seems like there's a difference of opinion. I'm travelling to Moab, Utah in June for an extended weekend of exploring many of the trails out there. As many of you may know the scenery is spectacular and I'm excited to get some great footage. With that said, my question is this, since there are many desert canyons there, if I descend into one and go down say 50-100ft below the recorded takeoff altitude, how can I expect, if anything, for the drone to respond? I'll be flying a Mavic Air1.

One other thing you might want to keep in mind. I gather its not unusual to experience weird air currents when descending into a valley. You wouldn't want a flyaway. Have fun.

 

[RkyMtnHigh]

One other thing you might want to keep in mind. I gather its not unusual to experience weird air currents when descending into a valley. You wouldn't want a flyaway. Have fun.

Oh I have thought of that. I live in the Rocky Mountains and the winds can be pretty unpredictable. Thanks for the heads up though!

 

[RkyMtnHigh]

I have a Mav Air 2. I don't have a MAV air 1. On the Mav air 2 l just see a negative altitude read out. No changes occur otherwise. I fly off a 5 story building every day. Then I fly below my starting point. Nothing changes except the altitude indicator is negative. That's all. Maybe the Mav Air 1 isn't getting firmware updates to eliminate this limitation? I don't know. I guess, do what the other pilots do, turning off downward sensors. Good Luck.

Thank you, I appreciate the info! Happy and safe flying!