I flew over a body of water today and noticed the Altitude readouts at the bottom of the screen dipped down into the minus/negative digits!

As a results, I could NOT effectively judge how far above the water I was flying!

Can someone/DJI explain this phenom?

It all depends on your take off point.  So, if say for instance you are above the body of H2O 10 feet at take off, then fly "down" to the H2O, as you go "below" your take off point the readings will be in the negatives.  Yes, it is hard to effectively judge how far above the water you are but as of now, there really is no "solution" to this other then user judgement.

ProQuad Posted at 2017-2-15 21:04
It all depends on your take off point.  So, if say for instance you are above the body of H2O 10 feet at take off, then fly "down" to the H2O, as you go "below" your take off point the readings will be in the negatives.  Yes, it is hard to effectively judge how far above the water you are but as of now, there really is no "solution" to this other then user judgement.

I get it.  I'll have to launch at water side to get a more effective readout.  In any case, referring to the current altitude readouts seems rather pointless.  I would have thought that the craft would have the capability of tracking your altitude above the ground/water at which you are currently flying.  Or at least the ability to re-set it randomly when needed.  Any apps other than go app 4 that might do this?

There are two read outs.
One is the altitude referenced to the starting point.

The other one is the ground clearance. You want to look for the latter.

See clearance in the lower left corner - since this is from the ultrasonic sensors on the bottom of the craft, it only works when closer to the ground (or water):

Egika Posted at 2017-2-16 01:06
See clearance in the lower left corner - since this is from the ultrasonic sensors on the bottom of the craft, it only works when closer to the ground (or water):
[view_image]

Thanks for your reply.  So you have to reference the RC panel.  Is the ground clearance displayed in the go app 4?

The distance to the ground information is just available if the bottom facing sensors are active (VPS). From what I read, it's recommended to deactivate them over water, any opinion on that?

I successfully use it over water. Why should I deactivate the sonar?
Could you point me to where it recommends to deactivate them?