400' AGL... off the top of a hill

[FormerMember06292019_2]

I live in flat-land USA these days so I haven't a convenient way to test this.

Given I am on top of a hill at least 400' above the surrounding terrain and I lift off straight up... my Mavic 2 will top out just under 400' AGL from my launch point. I then move the drone in any direction. And my AGL will increase in direct relation to the decreasing elevation of the hill.

Does the software/internal GPS firmware take this slope into account and cause the drone to descend or otherwise alert the user the drone is above 400' AGL?

 

[Thomas B]

I live in flat-land USA these days so I haven't a convenient way to test this.

Given I am on top of a hill at least 400' above the surrounding terrain and I lift off straight up... my Mavic 2 will top out just under 400' AGL from my launch point. I then move the drone in any direction. And my AGL will increase in direct relation to the decreasing elevation of the hill.

Does the software/internal GPS firmware take this slope into account and cause the drone to descend or otherwise alert the user the drone is above 400' AGL?

No it does not. Your take off is registered as the zero point in the aircraft. Going down the slope of the hill will produce negative numbers.

The drone will not automatically follow any terrain.

 

[AnzacJack]

This comes up soooo often. Perhaps we could have a stickie explaining how the drone detects and behaves to altitude in relation to take off point?

 

[Thomas B]

This comes up soooo often. Perhaps we could have a stickie explaining how the drone detects and behaves to altitude in relation to take off point?

Or a sticky with a link to the manual?

 

[kensteele]

you will be in violation if you take off from that point and go uphill.

 

[Meta4]

you will be in violation if you take off from that point and go uphill.

??? .. Perhaps you can clarify that?
He's on the top of a hill - it's hard to go up hill from there.
There's no regulation anywhere against launching from a hilltop.

 

[THE CYBORG]

The top of a hill is ground zero regardless of altitude above sea level it happens to be.

 

[Starz]

you will be in violation if you take off from that point and go uphill.

Wow.

 

[AMann]

Some test questions:

I. You are on top of a 400’ hill, and want to fly up another 400’ above it. The airport in the valley 400’ below you has Class E airspace starting at 700’ above it and extends over your hill. Can you fly another 400’ up from the top of the hill and still be in uncontrolled airspace?

 

[BD0G]

Here is the right answer. Show me the sectional for the exact area you describe. Oh, and a current check for TFR's in the area. Whats the wind like at those upper elevations? Are there Kabatic winds in effect?
How much visibility is there? Is this during low hanging clouds or fog?
Are there people below me that I will be flying directly over?

Each and every flight is situational and can even change drastically during flight.

Am I flying as a Part 107 Licensed Pilot or Recreational and have either used LAANC (Part 107) or contacted ATC to obtain approval to fly into the Class E Airspace?

 

[kensteele]

you will be in violation if you take off from that point and go uphill.

??? .. Perhaps you can clarify that?
He's on the top of a hill - it's hard to go up hill from there.
There's no regulation anywhere against launching from a hilltop.

yep i mis-read too fast his statement when i saw the word "elevation"....then i started thinking he was on the hill and above him uphill is over 400 and below him downhill is under 400. 99% of the hills are like that since no hilltop is exactly at 400. but i see he said tip top (it's even in the title lol).

anyway i should revise my statement to "you will be in violation [of faa rules] if you take off from that point and ascend any further." yes it's off topic since he talking about his software but still a true statement nonetheless, correct?

 

[Meta4]

anyway i should revise my statement to "you will be in violation [of faa rules] if you take off from that point and ascend any further." yes it's off topic since he talking about his software but still a true statement nonetheless, correct?

If you said that, it would be incorrect as well.
If he launches from a hilltop that is 400 ft above sea level, he can climb another 400 feet and still be within regulations.
How do you think people fly at Denver?

 

[kensteele]

Wow.

i know, crazy isn't it? ?

 

[tcope]

This comes up soooo often. Perhaps we could have a stickie explaining how the drone detects and behaves to altitude in relation to take off point?

Maybe if the search feature of the forum did not cost so much to use....

 

[kensteele]

If you said that, it would be incorrect as well.
If he launches from a hilltop that is 400 ft above sea level, he can climb another 400 feet and still be within regulations.
How do you think people fly at Denver?

yes i'm probably confused on this. it's 400 ft agl. got it.

so help me understand, what does "400 ft agl off the top of a hill" means? does that mean you're at 400 agl while you are on the top of the hill?

eta: never mind, got it. had to keep re-reading it. it's flat here, we don't have hills. op said he took off and went all the way up to 400 agl and the moved off. ok.

 

[AnzacJack]

Or a sticky with a link to the manual?

Yep, I was trying to be nice. ;-)
I know some of us have extensive aviation experience, but this AGL thing isn’t rocket science

 

[Meta4]

so help me understand, what does "400 ft agl off the top of a hill" means? does that mean you're at 400 agl while you are on the top of the hill?

AGL anywhere means height above ground level.
That's the ground directly below the drone.
Not the ground at sea level, not the ground at the bottom of the hill or anywhere else.
It's directly below the drone.

 

[kensteele]

AGL anywhere means height above ground level.
That's the ground directly below the drone.
Not the ground at sea level, not the ground at the bottom of the hill or anywhere else.
It's directly below the drone.

sure. got it now. thanks.

 

[Bob1956]

I have a somewhat related question. Wondering how the drone determines altitude. I’m in northern WV and SW PA, it’s all hills. If I take my drone to 400 ft will I collide with an up slope if I travel far enough? Or will it stay 400 ft above the ground below it? For this exercise , not watching the camera view, just the altitude indicated.

 

[BigAl07]

I have a somewhat related question. Wondering how the drone determines altitude. I’m in northern WV and SW PA, it’s all hills. If I take my drone to 400 ft will I collide with an up slope if I travel far enough? Or will it stay 400 ft above the ground below it? For this exercise , not watching the camera view, just the altitude indicated.

It's not "following terrain". If the terrain rises 400' your aircraft will strike the terrain. It uses the takeoff point as an absolute reference and knows nothing more.