Hi

Just wondering, as I set of to fly today near the ocean - I started about 14m above sealevel.
As i descended the drone furthe towards the sea, it showed a negative height since i started
the flight at an higher altitude. - but no problems

Can this influence the phantom or the flight it self negatively? Except from chrashing in the sea
if solely relying on flight data shown on the display of course

Regards!

The altitude that you are descending was below that the point that you start to take off? When you take off, the drone assume that is 0 ground level. And below of this it will make negative.

It will not affect your flight.  I wouldn't get too close to the surface of the water tho.  Begging for a disaster.

The altitude shows on the app is the relative altitude of the takeoff point. For the influences, as for what I can tell now are the following: pay attention to the return to home altitude that you set, it is also the relative altitude of the takeoff point, don't mix that and thought it might be the total altitude the drone will fly; intelligent flight modes can not be used when the app showing a negative value.
For the flight and the drone itself, it doesn't seem to have negative influences. No worries, but fly safely.

DJI Thor Posted at 2017-10-13 08:16
The altitude shows on the app is the relative altitude of the takeoff point. For the influences, as for what I can tell now are the following: pay attention to the return to home altitude that you set, it is also the relative altitude of the takeoff point, don't mix that and thought it might be the total altitude the drone will fly; intelligent flight modes can not be used when the app showing a negative value.
For the flight and the drone it self, it doesn't seens to have negative influences. No worries, but fly safely.

Tanks for your reply.

So if I understand it correctly, e.g., i start flying from a point 20 meters above sealevel, have the RTH height set to 30. I fly "down" to 10 meters above sealevel and lose connection. The p4a will then rise 40 meters in total height, to achieve the 30 m RTH height correct?

ALABAMA Posted at 2017-10-13 07:58
It will not affect your flight.  I wouldn't get too close to the surface of the water tho.  Begging for a disaster.

Yep, the pulse always rise a notch when flying above water

allyssongemelli Posted at 2017-10-13 07:31
The altitude that you are descending was below that the point that you start to take off? When you take off, the drone assume that is 0 ground level. And below of this it will make negative.

Thanks! Is there any way to "reset" the height in-flight? as stated in a comment below, the intelligent flight modes will not work with a negative height value...

Works this way. If you are 20' above sea level, it will count 0 the ground level. So if you go high 30 m you are going 30m high from you start point. It doesn't matter the correct altitude like 20' above sea level. The start point continues to be 0.

sonnavindDF Posted at 2017-10-13 12:04
Thanks! Is there any way to "reset" the height in-flight? as stated in a comment below, the intelligent flight modes will not work with a negative height value...

No, you cannot reset the height in flight. But if the negative height bothers you, go down and start from sea level.

sonnavindDF Posted at 2017-10-13 12:02
Tanks for your reply.

So if I understand it correctly, e.g., i start flying from a point 20 meters above sealevel, have the RTH height set to 30. I fly "down" to 10 meters above sealevel and lose connection. The p4a will then rise 40 meters in total height, to achieve the 30 m RTH height correct?

Aloha sonnavind,

     Hey, what is this, math class!  Sneaky!  We always said we would never need this stuff in the real world.  Are you a teacher spying on us and setting us up for more math!

Aloha and Drone On!

sonnavindDF Posted at 2017-10-13 12:04
Thanks! Is there any way to "reset" the height in-flight? as stated in a comment below, the intelligent flight modes will not work with a negative height value...

Aloha sonnavind,

     As Geebax says, you can go down to the beach and land on a hard surface.  Shut off the motors and restart them.  You will now have a new recorded home point and a zero altitude from that take-off location.

    I tried creating a waypoints mission with a waypoint at an altitude below my take-off point and the DJI GO 4 app stated that it would not register that waypoint because it is a negative altitude.  Bummer, it would have been a neat course.  

     Litchi will register negative waypoints, but you have to figure out their altitude measurements first.  I am still working on it.  Not real easy that one.  But, I think Litchi takes their ground level altitude measurements from Google Earth.

    Hope this helps!

Aloha and Drone On!

sonnavindDF Posted at 2017-10-13 12:02
Tanks for your reply.

So if I understand it correctly, e.g., i start flying from a point 20 meters above sealevel, have the RTH height set to 30. I fly "down" to 10 meters above sealevel and lose connection. The p4a will then rise 40 meters in total height, to achieve the 30 m RTH height correct?

Yes, that's correct.

I fly in the mountains where I live. Sometimes I fly one or 2 hundred meters below home point.  Sometimes I fly 500m above home point.

The drone doesn't care. Just remember if you RTH the drone will stop forward movement and fly up to RTH level then return home as long as you have no stick inputs.