Can I set ALTITUDE above mean sea level instead of HEIGHT above ground level.

[RickAung]

I often fly my Mavic Pro 2 from a high point near the sea and it reads height above take-off point. I would like to descend closer to the sea to video boats etc. Is there any way to change the setting so it reads altitude, please? If not any tips as to how to descend the drone without getting its feet wet? Thanks

 

[BigAl07]

That's a negative. Take Off Point is ground ZERO. You can change the Home Point but the Height stays at the original point IIRC.

 

[msinger]

The altitude displayed at the bottom of DJI GO is always the estimated altitude above the takeoff point. There is no way to change that functionality.

If not any tips as to how to descend the drone without getting its feet wet?

Fly within VLOS so you can clearly see the aircraft's location at all times.

 

[RickAung]

That's what I thought. As a professional pilot, we used altitude as a reference after take-off and thought it would be useful information for the drone. All I can do then is note my altitude from GPS before take-off and then not descend more than that figure when over the sea?

 

[RickAung]

The altitude displayed at the bottom of DJI GO is always the estimated altitude above the takeoff point. There is no way to change that functionality.


Fly within VLOS so you can clearly see the aircraft's location at all times.

Yes, I can see it but difficult to judge how high above the water it is!

 

[msinger]

Yes, I can see it but difficult to judge how high above the water it is!

Maybe stand closer to the water then?

 

[PhantomFandom]

Just like a manned airplane, your drone calculates altitude based on barometric pressure. Therefore it can only know AGL and not MSL altitude. Trying to fly based on altitude from GPS is a risky proposition as well since GPS will lag, you can have signal loss, and it cannot give you the precision needed to fly "close to the water". You also have other factors like waves and tide.

Unless you have a very accurate radio altimeter, your best guide is your sense of vision. Just too risky in any case to get too close to the surface of an ocean.

 

[sar104]

That's what I thought. As a professional pilot, we used altitude as a reference after take-off and thought it would be useful information for the drone. All I can do then is note my altitude from GPS before take-off and then not descend more than that figure when over the sea?

If your takeoff elevation is being determined by GPS then bear in mind that it could be 10 m or so off even with plenty of satellites locked, and also that calculated barometric altitude change assumes a standard atmosphere. If you are going to descend really close to the water then combined with tidal variations, this is not going to be accurate enough and you are better off gauging the height visually.

 

[RickAung]

Maybe stand closer to the water then?

Not possible hence the question

 

[Mossiback]

It will always read height in relation to the position where the MP was turned on. When launching from a high point and dropping down it will just show height in negative numbers. Even if you could change to altitude, that would not keep it from hitting the water.

 

[msinger]

Not possible hence the question

In that case, the best thing you can do is watch the "VPS" altitude at the bottom of DJI GO. That will show the distance between the bottom of the aircraft and water below. That value is not always 100% accurate when flying over water, so I wouldn't recommend using it to fly within a few feet of the surface of the water.

 

[gnirtS]

Altitude above mean sea level isnt going to help you fly closer to the water - the clue is in the name. Its an average height not an actual height so can vary significantly up and down over a local area.
Add that to the barometer not being particular accurate and its a bad idea.
VPS may give some guidance provided the water isnt too smooth.
But ultimately, you need to watch with your own eyes where the thing is above the surface.

 

[AMann]

Maybe stand closer to the water then?

He’s got to hit it between the wave troughs and crests to be accurate, Otherwise if he waits when the water is going out to its lowest point, he’ll actually be measuring a trough, which is below sea level a little bit. That may be bad for the drone if he flies too low and still thinks there’s some altitude.

 

[Meta4]

I would like to descend closer to the sea to video boats etc. ... If not any tips as to how to descend the drone without getting its feet wet?

All I can do then is note my altitude from GPS before take-off and then not descend more than that figure when over the sea?

Why would you not descend to get closer?
There's no problem descending below launch point and if that's what you need to do to frame your shot, that's what you have to do.
Just keep an eye on how far above the water the drone is from what it's camera is showing you.
If you are shooting boats, that gives you a good visual reference to where sea level is and it's better than any numbers on your screen .

I launched from a 100 ft cliff but had no trouble shooting this this:

 

[gnirtS]

Ive operated at a -800ft altitude before now after a cliff launch. The mavic doesnt care. Its just a zero reference and for the operators convenience.
Ultimately if you can see your drone and see the screen you should be flying it that way and not relying on inaccurate, non precision instruments.

Also, we get a 32ft range between high and low tide (without atmospheric effect extras). Good luck flying at a mean sea level there...

 

[RickAung]

Why would you not descend to get closer?
There's no problem descending below launch point and if that's what you need to do to frame your shot, that's what you have to do.
Just keep an eye on how far above the water the drone is from what it's camera is showing you.
If you are shooting boats, that gives you a good visual reference to where sea level is and it's better than any numbers on your screen .

I launched from a 100 ft cliff but had no trouble shooting this this:

Great photo. Yes, I was thinking I would descend to get a photo, hopefully as good as yours. IF I knew my altitude was say 200 ft above sea level on launch I would not descend to a figure greater than say -180 ft. when over the sea. I have noted the other useful comments here reference the inaccuracy of GPS for height. Thanks everyone

 

[Meta4]

IF I knew my altitude was say 200 ft above sea level on launch I would not descend to a figure greater than say -180 ft. when over the sea.

I never worry about numbers. How are you going to know the altitude of your launch point anyway?
I just use the boat I'm photographing as my guide.
It's easy to tell if you are above the masthead or below the level of the lifelines.
And if you are getting lower than the lifelines, you are probably too close to the water.

 

[Meta4]

...

If you have the horizon in the picture, that is also a big help.

If the boat's cabin top is below the horizon .. the drone is higher than the cabin top.
If the cabin top is above the horizon ... you are lower than the cabin top.
That's obviously more important when dealing with smaller vessels than big ones.

In the second pic, the drone is lower than the top but still higher than the railing, so it's still a safe distance from the water.

 

[Cymruflyer]

If the OP is watching what he is doing, as in the drone plus the screen, I can't see any problem as to situational awareness as to how high above the water the drone is. With those two views for reference, there could not be a point that he can't tell how high above the water he is. In the same way that if you are sitting in the aircraft, you can easily tell where you are above the water by viewing the horizon.

Unless, which has been stated, that might be a perfectly smooth lake, then with that glassy mirror effect it can be impossible to tell your height above the water, if the shore line is a fair distance away from you. The only way to tell in such a situation is if you can see a disturbance on the water surface such as a water foul paddling along it.

If the OP wishes to photograph boats as he states, he should easily be able to see his height above the water, without any altitude numbers as a reference.

 

[RickAung]

If you have the horizon in the picture, that is also a big help.

If the boat's cabin top is below the horizon .. the drone is higher than the cabin top.
If the cabin top is above the horizon ... you are lower than the cabin top.
That's obviously more important when dealing with smaller vessels than big ones.

In the second pic, the drone is lower than the top but still higher than the railing, so it's still a safe distance from the water.

Great photos. Thanks, I am so glad I started this thread!