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Altitude

Newguy126

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New guy with a few flight behind me. Question is how does the a.c. Know it's altitude? My understanding is that if I set a max altitude and fly towards a hill that is higher than that it would hit the hill. It doesn't know how high it is above the ground, right? Does it have barometric sensing or use gps for altitude?
 
Barometer, so it can 'wander' a bit during a flight.
Your understanding is basically correct in that it could fly into something but the behaviour may be modified to some extent by sensors, you need to post a model for specific details
 
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The altitude always will be calculated base in the home point location or (take off location). If you set for example max altitude 400FT down the hill. You are going to fly to the hill and assuming is a 600FT toll hill, you are going to crash (hypothetically) since you set the maximum altitude at 400FT. Will be nice if DJI include sensors to measure the ground level.
 
once the AC is higher than 35ft above the ground then the downwards facing sensors no longer come into play the drone relies on a barometer to ascertain air pressure to know its altitude ,but the altitude displayed on the APP screen is only relative to the place it took off from
and it will change considerably due to changes in air pressure and it is not an accurate reading after the drone has flown away from the take off point
and indeed if you fly from a high point and then travel down into a valley then you will get a negative reading
 
I know this might be a stupid question as I am sure of the answer already, but just want to check. Dose that mean if you take off from high ground and fly over a valley, you can fly over the 120m/400ft limit ? if the valley floor is more then 120m/400ft below ?

Did not even think about this before I read this post, so just making sure 100% that I am sure before flying
 
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I know this might be a stupid question as I am sure of the answer already, but just want to check. Dose that mean if you take off from high ground and fly over a valley, you can fly over the 120m/400ft limit ? if the valley floor is more then 120m/400ft below ?

Did not even think about this before I read this post, so just making sure 100% that I am sure before flying
That is correct.
 
I know this might be a stupid question as I am sure of the answer already, but just want to check. Dose that mean if you take off from high ground and fly over a valley, you can fly over the 120m/400ft limit ? if the valley floor is more then 120m/400ft below ?

Did not even think about this before I read this post, so just making sure 100% that I am sure before flying
no you cant the max height is above the ground wherever the drone is flying ,so you would have to descend to stay legal
but in reality you would be over the permitted height allowed if you just flew straight out over the valley
 
no you cant the max height is above the ground wherever the drone is flying ,so you would have to descend to stay legal
Thanks for answer, that was what I was concerned about, as was not sure if drone would descend on its own to stay under 120m if ground dropped.
 
Outside the range of the downward looking sensors the drone has no knowledge of its height above the ground directly beneath it, so, yes by flying outwards from a hill top, you can physically break the apparent ceiling.
HOWEVER the 400ft ceiling is, in many place, "law" and is not so easily cheated. In the UK you ARE legally limited to 400ft above the ground beneath the drone. So flying out over your valley from 400ft above the high ground you would need to descend to remain within 400ft of the ground and legal.
Conversely if you take off from the bottom of a 500ft hill and fly up the hill you could legally reach 900ft above the take off point when you are 400ft above the hill top.

as shown in Where you can fly | UK Civil Aviation Authority

The 400ft ceiling in the app is not absolute and can be raised, ...... to 500m in most cases, the latter is a 'hardwired' ceiling in the many DJI softwares
 
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I'm not suggesting it's not true because I have no idea how it works but the drone is already using GPS to know it's position, why would they use a barometer to measure altitude? GPS will provide an accurate altitude within a few feet. A barometer will not be as accurate as GPS.
 
GPS can tell where you are, not how high your drone is. That is why if you lose your GPS your drone will still hold its Hight (Barometer), but can drift in the wind as it dose not know where it is meant to be.
 
GPS heights are woefully inaccurate. Look in the logs, I have 'been' at something like 70ft above or below sea level (I can't remember which it was) when the drone was 1ft above sea level at the beach.
I have seen heights in a DSLR's location data that were questionable and that is GPS derived too.
 
But saying that:

Galileo is intended to provide horizontal and vertical position measurements within 1-metre precision

Not sure if DJI drones can use galileo or how well it works ?
 
Galileo is intended to provide horizontal and vertical position measurements within 1-metre precision

Not sure if DJI drones can use galileo or how well it works ?
The new Mavic Mini is DJI's first consumer drone to use Galileo as well as GPS and Glonass.
But even the most accurate GPS still won't provide altitude above terrain.
 
The new Mavic Mini is DJI's first consumer drone to use Galileo as well as GPS and Glonass.
But even the most accurate GPS still won't provide altitude above terrain.

I'd be shocked if it didn't also use the new BeiDou constellation as it's owned by China. I thought the drones used uBlox GNSS chips, and those do support that constellation.
 
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Every time I come on Forums, I learn something new, in a way glade drone has been delayed. As in the last few days, I have learnt so much :)
 
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I'd be shocked if it didn't also use the new BeiDou constellation as it's owned by China. I thought the drones used uBlox GNSS chips, and those do support that constellation.
You could just check the specs.
They say: Global Navigation Satellite System (GNSS): GPS+GLONASS+GALILEO
 
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