Mavic Air behavior on top of buildings or cliffs (and water)?

[dwallersv]

That's not what the OP is talking about, though.

True.

So what?

 

[dwallersv]

Yes, me too! I find that very disconcerting in the least. I fly in AZ with a bazillion steep valleys & deep canyons to explore. With all the techy abilities the MP has you'd think it could 'ping' your correct altitude or obtain it from GPS.

it has GPS altitude, the control firmware just ignores it, probably because of the potentially large error.

Still, it would be nice if they made the data available in the telemetry display.

 

[Prismatic]

True.
So what?

So that’s called “thread drift”, and it often sends thoughtful discussions veering off into the weeds. It’s a common prob—Hey! Squirrel!—, but generally considered poor etiquette in forums of this kind.

 

[Drgnfli]

it has GPS altitude, the control firmware just ignores it, probably because of the potentially large error.

Still, it would be nice if they made the data available in the telemetry display.

The GPSs I've owned from Garmin are usually accurate within 6 feet. That would be more accurate than the present reading when dropping into a 500' canyon. Trying to determine how high you are at that distance while VLOS is next to impossible. Present use of the altitude is only a check to see when you are about to land where you took off from...

 

[dwallersv]

So that’s called “thread drift”, and it often sends thoughtful discussions veering off into the weeds. It’s a common prob—Hey! Squirrel!—, but generally considered poor etiquette in forums of this kind.

Well, actually it wasn't. I was correcting misinformation posted.

Had it vectored off into a side-discussion of available positioning technologies, that would have been "drift".

Kinda like this very discussion.

 

[dwallersv]

The GPSs I've owned from Garmin are usually accurate within 6 feet. That would be more accurate than the present reading when dropping into a 500' canyon. Trying to determine how high you are at that distance while VLOS is next to impossible. Present use of the altitude is only a check to see when you are about to land where you took off from...

You're referring to 2D position information. That is pretty accurate.

For reasons of geometry, surface altitude calculations have much bigger errors, often as much as 100'. Far too inaccurate for real-time flight decisions, where knowing the altitude matters.

 

[Prismatic]

...
For reasons of geometry, surface altitude calculations have much bigger errors, often as much as 100'.
...

The geometry does indeed make determining altitude more problematic, that’s definitely true. But I believe national security is the primary reason altitude is unreliable; we get a slightly scrambled signal. Military GPS is not so encumbered, allowing for extremely accurate 3D positioning.

 

[dwallersv]

The geometry does indeed make determining altitude more problematic, that’s definitely true. But I believe national security is the primary reason altitude is unreliable; we get a slightly scrambled signal. Military GPS is not so encumbered, allowing for extremely accurate 3D positioning.

My knowledge of this is dated, as I haven't followed the issue since the distortion was removed 10-15 (or more) years ago that screwed accuracy to no better than 50' or so.

I was aware that the military had centimeter accuracy available, but it was my understanding it was a different system of birds, not crippling the civilian signal. Do you have any other info on this?