Mini 2 altimeter operation?

[Skwirl]

While flying yesterday I noticed the altimeter reading isnt a "live" number.
Is that correct?
I think what's happening is, the altimeter reading is based off of where you take off.
I asked cause I was a lot closer to the ground than what it said. I flew the drone up a small hill around some hay bales and when I turned camera down to get an idea of height, i was just above the ground but the altimeter read 2 meters or so.
After some head scratching, I came up with the aforementioned scenario.
I'm hoping to get some more flight time on Sun to check again.
Thought I'd ask here in the meantime.
So, am I having a brain fart?

 

[NOLADG]

Yes, the altimeter is not "live" but based on where you take off. It can also change based on the air pressure changes, so do not consider it to be super accurate.

 

[Deleted member 103366]

The height is based on pressure changes measured by a barometer, the zero point is set as, presumably, the air pressure at the take off point. Ignoring the maximum working height above sea level (due to air density) the two user set ceilings, RTH height and Maximum Height, and the hardwired in maximum height (500m) are all relative to the take off point.

 

[Skwirl]

Thanks fellas. Ill make sure to remember that. It would be embarrassing to say I flew into the ground, lol.
It would be great to have a functional altimeter though. Are the other dji drones like this to?

 

[old man mavic]

@Skwirl actually with regards to flying into the ground the Mini 2 will follow the terrain when it is close to the ground ,you can check this out by flying slowly up a slope towards yourself and you will see the drone rise ,the sensors on the bottom of the drone are what makes it possible ,it only works if you fly up hill does not work descending down a slope ,if you hover at eye level and then put your hand directly under the drone it will rise up because the sensors see your hand as the ground ,the sensors work till about 16,to 20ft altitude then the altimeter takes over to determine the height you see on the screen
you may notice two height readings at the bottom of the screen when you first take off one is from the downwards facing sensors ,and as you climb you will notice that the one on the left of the screen will go to zero once you are out of sensor range

 

[Meta4]

It would be great to have a functional altimeter though. Are the other dji drones like this to?

The height reading on your screen is live, but it's showing the height of the drone relative to the launch point.
The drone has no sensor capable of measuring the height of the drone relative to the ground below it.
Yes ... all DJI drones are that way.
You might be surprised to find that so are real airplanes too , except their altimeters show height above sea level (which could be even more confusing when close to terrain).

Radar altimeters are too heavy for drones and too expensive to be commonly fitted to most general aviation aircraft.

 

[Skwirl]

The height reading on your screen is live, but it's showing the height of the drone relative to the launch point.
The drone has no sensor capable of measuring the height of the drone relative to the ground below it.
Yes ... all DJI drones are that way.
You might be surprised to find that so are real airplanes too , except their altimeters show height above sea level (which could be even more confusing when close to terrain).

Radar altimeters are too heavy for drones and too expensive to be commonly fitted to most general aviation aircraft.

Thanks, excellent explanation.
My simple way of thinking was an altimeter would read how far up you are and change as needed. While it does do that, just not how I thought it worked.
I now understand the operation of it.
Dang newbies, lol.