I'm going to be travelling threw the Rocky Mountains and wondering if I'm on a Cliff at 2000 feet, HOW will my P3S will react to the 2000 ft drop when it is flown over the Cliff, understand wind turbulence but nothing about the effect instantaneous drop, what will the height meter record???

It will record a negative value, but it has no effect on your flying. It will not even know the 2,000 foot drop is there, all it knows is the point it took off from. So if you fly down 100 feet from where you took off, it will register -100.

I flew my Phantom 3 Standard when I was at the top of a mountain in New Zealand and it was fine. Although the winds were pretty strong up there so it was a bit scary, got some awesome footage, if a bit shakey

fansd77b4cd0 Posted at 2017-7-21 16:36
I flew my Phantom 3 Standard when I was at the top of a mountain in New Zealand and it was fine. Although the winds were pretty strong up there so it was a bit scary, got some awesome footage, if a bit shakey

Also be sure to post the footage on this thread, i'd love to see it

If it has to auto land you will be ok since the motors will not stop until there is no chance in altitude sensed. But if it tries to do an RTH and your'e flying 200 feet lower than your take off altitude....... hope you have some rope with ya.

Betamace Posted at 2017-7-21 19:57
If it has to auto land you will be ok since the motors will not stop until there is no chance in altitude sensed. But if it tries to do an RTH and your'e flying 200 feet lower than your take off altitude....... hope you have some rope with ya.

if it tries to do an RTH and your'e flying 200 feet lower than your take off altitude....... hope you have some rope with ya.

Why?
The designers were smart enough to make sure that negative altitude makes no difference to the Phantom or RTH.
You have your RTH set to X metres above the level of your launch point ... and that's what the Phantom would climb to.
The same X metres above launch point that it would climb to wherever RTH is initiated.

Yeah you will be fine - I've done this a few times with no trouble. RTH shouldn't be a problem either. PS3 understands the negative alt. As you say just watch out for turbulence and be sure to share the footage! :-) would be awesome to see! Good luck and have fun!

Aloha Slayer,

     Aside from the suggestions of the others, one thing I noted is that negative altitudes will not record for waypoints and other barometric based settings.  So, you can forget about those types of missions in negative altitude.  Positive altitude will give you no problems though.

     Looking forward to the videos and photos!

Aloha and Drone On!

Labroides Posted at 2017-7-21 22:57
if it tries to do an RTH and your'e flying 200 feet lower than your take off altitude....... hope you have some rope with ya.

Why?

I admit I was wrong. After doing a little research I found  that if if RTH is initiated when a negative altitude is sensed, the drone will first ascend to "0" altitude before beginning the RTH.  Probably loss of signal can be expected when flying below take-off altitude as in launching off from a cliff and flying below LOS..

Betamace Posted at 2017-7-22 13:05
I admit I was wrong. After doing a little research I found  that if if RTH is initiated when a negative altitude is sensed, the drone will first ascend to "0" altitude before beginning the RTH.  Probably loss of signal can be expected when flying below take-off altitude as in launching off from a cliff and flying below LOS..

Your research is still wrong.
Loss of signal is not expected just because your Phantom is lower than takeoff point.
And on RTH the Phantom doesn't ascend to zero before returning home.
It ascends to the RTH height and then returns home.

There's nothing special or unusual about flying from a high point with the Phantom lower than the pilot.
It won't cause any weird or difficult situations.

I did a flight once on an island in the Mediterranean Sea, on a cliff with very windy conditions. The Phantom did just fine. Don't worry about the drop, but consider the wind, especially save some battery for landing as the shaking might take you a bit longer to come back and land safely.

So in summary,If I set my RTH to 200ft and then I take off from a mounain Cliff let's say 1500ft. The AC is flown over the edge and I drop it to about - 300 ft ( which is at 1200ft)and flu for a bit, then for some reason RTH is tripped. Your saying the AC will climb to 1700 ft then return to the Cliff which is at 1500ft (in a perfect scenario)  

Salmonslayer Posted at 2017-7-22 17:58
So in summary,If I set my RTH to 200ft and then I take off from a mounain Cliff let's say 1500ft. The AC is flown over the edge and I drop it to about - 300 ft ( which is at 1200ft)and flu for a bit, then for some reason RTH is tripped. Your saying the AC will climb to 1700 ft then return to the Cliff which is at 1500ft (in a perfect scenario)

With the Phantom all heights are relative to your launch point which is zero ft.
It doesn't matter whether you are talking about an altitude above or below you.
So any RTH will climb to the height you set ABOVE launch point.
Not above sea level, not above anything except above launch point because that's the only height your Phantom knows.
Every other height is relative to your launch point.

Is that clear enough?

Labroides Posted at 2017-7-22 20:07
With the Phantom all heights are relative to your launch point which is zero ft.
It doesn't matter whether you are talking about an altitude above or below you.
So any RTH will climb to the height you set ABOVE launch point.

PERFECT ! WELL SAID !  

now, phantom has a limit of 500meters ascend... I do not know how it will react if you plan to go over 500m down.. will it be able to come back up? (that's 1500ft, or so).. Keep that in mind....

Think I'll keep it well above the - 500, but thanks for the heads up on that

Salmonslayer Posted at 2017-7-23 18:18
Think I'll keep it well above the - 500, but thanks for the heads up on that

You can fly 1500m below launch point that is not the issue. The only issue would be if you have enough power left for RTH. The drone would climb to RTH height then return home.