Descending to altitude below launch point question

[Mandalorian]

I tried searching the forums for an answer to this question but didn't find one.

If I launch a Mavic Pro or Pro Platinum from a cliffside that is 200' above an adjacent valley floor, I'm assuming the Height indicator on the DJI GO app will indicate 0' (zero feet) at launch point (provided I've previously selected Imperial units and not metric).

If I descended the Mavic 150' down into the valley what would the app Height indicate? -150?

Thanks in advance for replies.

 

[Recoveryone]

Your logic is correct, it will simply read negative altitude. I at times fly flood control channels which are below the launch/take off point and the screen will just show your altitude in negative numbers.

 

[Mandalorian]

Your logic is correct, it will simply read negative altitude. I at times fly flood control channels which are below the launch/take off point and the screen will just show your altitude in negative numbers.

Thank you.

 

[RadioFlyerMan]

I tried searching the forums for an answer to this question but didn't find one.

If I launch a Mavic Pro or Pro Platinum from a cliffside that is 200' above an adjacent valley floor, I'm assuming the Height indicator on the DJI GO app will indicate 0' (zero feet) at launch point (provided I've previously selected Imperial units and not metric).

If I descended the Mavic 150' down into the valley what would the app Height indicate? -150?

Thanks in advance for replies.

Yes, that’s my experience while descending down from the top of the Porcupine Mountains.

 

[old man mavic]

I tried searching the forums for an answer to this question but didn't find one.

If I launch a Mavic Pro or Pro Platinum from a cliffside that is 200' above an adjacent valley floor, I'm assuming the Height indicator on the DJI GO app will indicate 0' (zero feet) at launch point (provided I've previously selected Imperial units and not metric).

If I descended the Mavic 150' down into the valley what would the app Height indicate? -150?

Thanks in advance for replies.

yes , but remember that there is a 150 ft exclusion zone from the valley floor ,if there are dwellings or people below you ,so if you went down 150 ft you would be too close to them

 

[OzzieHerr]

Here’s an extension to the question...say you descend 350’ from the launching point then the drone goes into RTH mode, will it climb all the way from -350’ plus the RTH altitude, thus potentially rising to more than 400’ AGL?

 

[Recoveryone]

Here’s an extension to the question...say you descend 350’ from the launching point then the drone goes into RTH mode, will it climb all the way from -350’ plus the RTH altitude, thus potentially rising to more than 400’ AGL?

Man I'm glad my wife a math teacher...……..at what point is your RTH taken from? point of take off. It's not the total distance travel, but the setting of your RTH. If your RTH is set at 120 feet AGL then your drone will climb to the height of 120 feet above AGL to reach its RTH starting point.

 

[Meta4]

If your RTH is set at 120 feet AGL then your drone will climb to the height of 120 feet above AGL to reach its RTH starting point.

There is no AGL .. the drone can't measure AGL (past 10 metres).
All heights are relative to the home point.

 

[old man mavic]

Here’s an extension to the question...say you descend 350’ from the launching point then the drone goes into RTH mode, will it climb all the way from -350’ plus the RTH altitude, thus potentially rising to more than 400’ AGL?

yes it will be more than 400ft AGL until it gets back over the home point on the top of the cliff,and in the case of the M2P it retraces its path back before it actually comes home

 

[OzzieHerr]

If your RTH is set at 120 feet AGL then your drone will climb to the height of 120 feet above AGL to reach its RTH starting point

Thanks for your reply but still confused. Say the drone is only 50’ AGL when it starts returning home, but still 250’ below the edge of the cliff where you started. Does it climb another 70’ (assuming you set your RTH at 120’ AGL) and continue to climb until it’s 120’ above it’s starting point before it descends to land? Or, does it simply retrace it’s path back, including the altitude profile? Sorry if my question is wordy...

 

[OzzieHerr]

There is no AGL .. the drone ca

yes it will be more than 400ft AGL until it gets back over the home point on the top of the cliff,and in the case of the M2P it retraces its path back before it actually comes home

That would make sense. Just want to make sure. Thanks for your reply.

 

[Meta4]

If your RTH is set at 120 feet AGL then your drone will climb to the height of 120 feet above AGL to reach its RTH starting point

Thanks for your reply but still confused. Say the drone is only 50’ AGL when it starts returning home, but still 250’ below the edge of the cliff where you started. Does it climb another 70’ (assuming you set your RTH at 120’ AGL) and continue to climb until it’s 120’ above it’s starting point before it descends to land? Or, does it simply retrace it’s path back, including the altitude profile? Sorry if my question is wordy...

The drone does not understand AGL.
All heights are relative to the home point.
It only knows that Home = zero.
It doesn't matter whether the drone is above or lower than the level of the home point, when you initiate RTH the drone will climb to the set RTH height above the level of the home point (unless the drone is already higher than the set RTH height).

If you initiate RTH, the drone wil immediately commence its RTH procedure.
If you lose signal, the drone will attempt to retrace until it regains signal - if your drone model has that feature.
Check your manual for details.

 

[OzzieHerr]

That seems to confirm what old man Mavic said. There are time similar threads below indicate some users can’t even descend below zero AGL to begin with, but there may be other reasons for that (National Park boundary, Geo Zones, etc). So I will just have to CAUTIOUSLY try it! Thanks to both for your responses. Wish you happy productive and safe flying!

 

[Meta4]

That seems to confirm what old man Mavic said. There are time similar threads below indicate some users can’t even descend below zero AGL to begin with, but there may be other reasons for that (National Park boundary, Geo Zones, etc). So I will just have to CAUTIOUSLY try it! Thanks to both for your responses. Wish you happy productive and safe flying!

You'd have to be pretty silly to program a drone to only fly higher than where it is launched from.
You'll read all kinds of things in forums, but not all are correct.
There's nothing to stop your drone descending lower than the home point.

 

[Thomas B]

Set altitude for RTH is always relative to TO point (0 altitude).

 

[Richard Fiske]

On another note then, I'm guessing that descending down, it wouldn't know where the new ground level was below you either.. is it then only the sensors on the bottom of the drone that would stop it smashing into the ground. You wouldn't have relenant telemetry readings...

 

[Meta4]

On another note then, I'm guessing that descending down it wouldn't know where the new ground level was below you either.. is it then only the sensors on the bottom off the drone that would so it smashing into the ground. You wouldn't have relenant telemetry readings...

It doesn't matter whether the drone is lower than or higher than it's launch point.
It never knows where the ground level is until it is within VPS sensor range.
The world is not pancake-flat and flying over higher and lower ground is completely normal.
Higher than or lower than makes no difference to telemetry either.