Lower Sensor, it's purpose?

[xunhui]

I've read through my user manual and I'm a little confused. What exactly does the lower sensor actually do? In flight I can hover over anything, building, tree or myself. But have yet to ever have any sort of warning, nothing. It's very obvious how the forward and aft sensors work. But just can't grasp what the lower sensors actually do, if anything.
I'm all ears, please enlighten this ignorant pilot.

 

[Meta4]

But just can't grasp what the lower sensors actually do, if anything

It's in what you pasted above:
The Downward Vision System and Infrared Sensing System helps the aircraft maintain its current position, hover in place more precisely, and to fly indoors or in other environments where GPS is unavailable.

 

[brett8883]

I've read through my user manual and I'm a little confused. What exactly does the lower sensor actually do? In flight I can hover over anything, building, tree or myself. But have yet to ever have any sort of warning, nothing. It's very obvious how the forward and aft sensors work. But just can't grasp what the lower sensors actually do, if anything.
I'm all ears, please enlighten this ignorant pilot.

View attachment 109084View attachment 109085

There are two sets of sensors on the bottom that work together but do slightly different things. The vision sensors use computer vision to hold precise position and measure distance to the ground but less precisely. The infrared sensors measure the distance to the ground which is more precise but has less distance range.

Both sensors work together to prevent a hard landing and keep you away from obstacles automatically. If you fly low over something like a table you’ll see that when it goes over the table it will pull up a little to avoid the table

 

[z28lt1]

By "lower" I'm assuming you bean bottom sensors? They do a ton, some of which you listed -- off the top of my head
1 - They maintain positioning when GPS is weak or unavailable
2 - The provide the ability to note the takeoff point and use precision landing
3 - At lower altitude, they help determine the height above ground
4 - They prevent you from flying down into something (ever try to land and notice when you get close the the ground the sensors keep it up for a tiny bit, making sure you want to land?)
5 - They attempt (maybe not super well) to determine if the landing area is a suitable place to land
6 - Not sure how much they are used by APAS with the ability to go under an object, but I would "guess" they play a part.

EDIT - noted some posts as I was typing mine, some diplicate stuff, sorry.

 

[xunhui]

I see that they help with maintaining my height but the avoidance has got me confused. I was hovering over a tree, slowly came down and nothing. At 1" nothing, no sound, no visual indication. I can rotate the drone and face the other part of the tree with it's forward and rear sensors, instant sound and visual indication.

4 - They prevent you from flying down into something (ever try to land and notice when you get close the the ground the sensors keep it up for a tiny bit, making sure you want to land?)

This does not happen, never has.

 

[brett8883]

I see that they help with maintaining my height but the avoidance has got me confused. I was hovering over a tree, slowly came down and nothing. At 1" nothing, no sound, no visual indication. I can rotate the drone and face the other part of the tree with it's forward and rear sensors, instant sound and visual indication.

4 - They prevent you from flying down into something (ever try to land and notice when you get close the the ground the sensors keep it up for a tiny bit, making sure you want to land?)

This does not happen, never has.

It should stop momentarily before touching down when landing manually. A tree is a bad example because it’s too irregular of a shape. Sensors can’t get a good read especially with the props whirling the leaves around.

I don’t know if MA2 has this option but this is called landing protection so check that you have it turned on. It may always be on though.

 

[old man mavic]

the downwards sensors are not the same as the forwards and rearwards anti collision sensors there primary roll is sensing the surface beneath the drone to know where the surface is to allow the drone to hover ,in the absence of GPS and they only work up to a certain height they also stop the drone from landing, and will warn you if they think the surface is unsuitable for a landing, they can be fooled by reflective surfaces such a water, and need some pattern on the surface to recognise for an accurate RTH, the tree you mentioned is not a solid structure so the sensors can not get a lock to stop the drone landing as stated above by @brett8883 one other thing to be aware of if you are flying in mist or fog and go above the mist or fog then the sensors can react to the water droplets in the mist or fog and think the drone is above solid ground and stop the drone from descending

 

[xunhui]

the downwards sensors are not the same as the forwards and rearwards anti collision sensors there primary roll is sensing the surface beneath the drone to know where the surface is to allow the drone to hover ,in the absence of GPS and they only work up to a certain height they also stop the drone from landing, and will warn you if they think the surface is unsuitable for a landing, they can be fooled by reflective surfaces such a water, and need some pattern on the surface to recognise for an accurate RTH, the tree you mentioned is not a solid structure so the sensors can not get a lock to stop the drone landing as stated above by @brett8883 one other thing to be aware of if you are flying in mist or fog and go above the mist or fog then the sensors can react to the water droplets in the mist or fog and think the drone is above solid ground and stop the drone from descending

Thank you old man mavic. With your and everyone's replies I have a better understanding of how the lower sensors actually work.

 

[Chris Mitchell]

Xunhui, I published a video a few weeks ago describing the downward sensors (vision and infrared) and how the are used during Mavic Air 2 Precision Landings. Have a look, it might add to your knowledge base:

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[hiflyer201]

the lower sensors land the drone for you. you pick the spot and the sensors land the drone. No skill needed. A little finesse helps.

 

[xunhui]

Xunhui, I published a video a few weeks ago describing the downward sensors (vision and infrared) and how the are used during Mavic Air 2 Precision Landings. Have a look, it might add to your knowledge base:

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Thank you... I watched all of your video and it did help with the understanding. I liked your "Manned Aircraft Nearby" in Chinese, wonder if I can change mine to Chinese?

 

[kidroc]

When you get a warning it’s unsafe to land that’s them working they do a lot more than the others sensors do. They help with height and positioning.

 

[Ben Anderson]

In low light conditions, the sensors determine your height above the ground and turn on the light for landing at around 5m above the ground.