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Max Take Off Altitude = 0
2318 20 2017-6-16
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Pagemakers
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Just purchased a Mavic Pro today. Only flown for a few minutes and about 6 flights. Max altitude so far 30 meters. However, when I look at the main flight records home page in the DJI app this drone reports a max take off flight altitude of 0.

My previous Phantom 3&4 show about 150m each.

Why is the Mavic showing zero?
2017-6-16
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Panaceabeachbum
lvl.3
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United States
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Mine shows, 246 meters even though I live at sea level
2017-6-16
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Pagemakers
lvl.3
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Is it max height you've attained in the flight or the actual take off altitude? Despite what it says I think it's the former.
2017-6-16
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Mcflying
Second Officer
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I live 5 meters below sea level and have no problems at all.
So i guess altitude of 0 means, from the point you start the engines.
2017-6-17
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Landbo
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Mcflying Posted at 2017-6-17 00:17
I live 5 meters below sea level and have no problems at all.
So i guess altitude of 0 means, from the point you start the engines.

Your guess is absolutely correct. Mavic can not measure in absolute heights as it does not know the correct height at the starting point. Therefore, all heights are relative to the take off points.  

Regards Leif.
2017-6-17
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Mcflying
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Well actually sometimes i read on the  remote "-1 meter"
2017-6-17
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Landbo
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Mcflying Posted at 2017-6-17 12:31
Well actually sometimes i read on the  remote "-1 meter"

The -1 meters are also sometimes on my controller after landing on the take off place is eg 41 meters ASL. The small inaccuracies can be attributed to errors in the software or hardware.

What is the height so if you take off from a place that is located eg +10 m ASL ?   

Regards Leif.
2017-6-17
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WolfgangStiller
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It doesn't tend to very very accurate. I am not sure if it's based on barometric pressure or GPS altitude but mine currently shows 15,500 feet but I have never taken off any higher than a bit over 14,000 msl.  If it's GPS altitude it could be because it grabs it's fix right after you first start up and from years of using a hand held GPS, I know this altitude often is way off and then minutes later will settle down close to the correct value.
2017-6-17
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Landbo
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WolfgangStiller Posted at 2017-6-17 13:20
It doesn't tend to very very accurate. I am not sure if it's based on barometric pressure or GPS altitude but mine currently shows 15,500 feet but I have never taken off any higher than a bit over 14,000 msl.  If it's GPS altitude it could be because it grabs it's fix right after you first start up and from years of using a hand held GPS, I know this altitude often is way off and then minutes later will settle down close to the correct value.

Mavic does not get any height from GPS because it's too inaccurate. The height of the vessel is calculated from the air pressure and is actually very accurate. For the same reason, all measured height is relative to your take off place.   

https://en.wikipedia.org/wiki/Barometric_formula

Regards Leif.
2017-6-17
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Pagemakers
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So why does mine show 0 for my Mavic? I was 70m above sea level for the few flights I've used it on.
2017-6-17
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WolfgangStiller
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Landbo Posted at 2017-6-17 14:05
Mavic does not get any height from GPS because it's too inaccurate. The height of the vessel is calculated from the air pressure and is actually very accurate. For the same reason, all measured height is relative to your take off place.   

https://en.wikipedia.org/wiki/Barometric_formula

Where did you learn that?  
2017-6-18
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Dennis.D
lvl.2
Flight distance : 47503 ft
Australia
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I have the same issue (http://forum.dji.com/thread-100496-1-1.html)
Following with interest.
2017-6-18
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Landbo
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It is common "GPS" theory. A great place to start learning will be here:  https://en.wikipedia.org/wiki/Global_Positioning_System   

Regards Leif.
2017-6-18
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Landbo
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Pagemakers Posted at 2017-6-17 16:09
So why does mine show 0 for my Mavic? I was 70m above sea level for the few flights I've used it on.

t's a bit hard and help you because you do not tell in which APP you find that text. I can not find it in DJIGO4, which I suppose you should use for your Mavic.

Regards Leif.
2017-6-18
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WolfgangStiller
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Landbo Posted at 2017-6-18 21:10
It is common "GPS" theory. A great place to start learning will be here:  https://en.wikipedia.org/wiki/Global_Positioning_System   

Regards Leif.

I meant how did you know that the Mavic doesn't use GPS but barometric presure.
2017-6-19
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Landbo
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WolfgangStiller Posted at 2017-6-19 05:24
I meant how did you know that the Mavic doesn't use GPS but barometric presure.

Oh yes. I'm absolutely sure when you do not get the height given in absolut meters/feet ASL (Above Sea Level).

Regards Leif.
2017-6-19
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WolfgangStiller
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Landbo Posted at 2017-6-19 10:10
Oh yes. I'm absolutely sure when you do not get the height given in absolut meters/feet ASL (Above Sea Level).

Regards Leif.

As that what you based your statement on?    In this case, the altitude we are talking about (max take off altitude) is supposed to be ASL/MSL. (elevation above see level). In my case, it shows as 15,500 ft (It is saying I took off that high above sea level not that high above the ground).
2017-6-19
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Landbo
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WolfgangStiller Posted at 2017-6-19 11:13
As that what you based your statement on?    In this case, the altitude we are talking about (max take off altitude) is supposed to be ASL/MSL. (elevation above see level). In my case, it shows as 15,500 ft (It is saying I took off that high above sea level not that high above the ground).

It's a little hard to answer your question when you do not want to tell where you read your numbers. DJIGO4 Vx.x.x and OS, thanks.

Have you ever take off with your drone from that height ?

Regards Leif.
2017-6-19
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WolfgangStiller
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Landbo Posted at 2017-6-19 13:52
It's a little hard to answer your question when you do not want to tell where you read your numbers. DJIGO4 Vx.x.x and OS, thanks.

Have you ever take off with your drone from that height ?

The flight in question (with the 15K elevation) was actually a take off at 14,100 ft.).  The number asked about by the OP, is what you can see for max take off elevation of the flight record page in DJI Go4.  
2017-6-19
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Landbo
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WolfgangStiller Posted at 2017-6-19 18:35
The flight in question (with the 15K elevation) was actually a take off at 14,100 ft.).  The number asked about by the OP, is what you can see for max take off elevation of the flight record page in DJI Go4.

Wolfgang, you have to understand it's very difficult and answer your questions when you do not want to tell where you'll find the "Max Take Off Altitude" and therefore I can only comment on general terms.

I know the height mentioned can NOT be found in the DJIGO4 APP for Android !!!

However, you yourself confirm that a GPS might not be so good at measuring heights as you have a difference of 15,500 - 14,100 ft, which is 1,400 ft or an error of around 10%. Again assumed the height comes from your phone's GPS.

The reason for coming to this conclusion is that you can not measure the absolute height Above See Level using a barometer without knowing the absolute air pressure at quota 0 on the spot the moment you make the calculation. When a plane sets its altimeter before take off, they ask the tower at which altitude the aerodrome is located and the absolute air pressure on the spot. When the two numbers are inserted into the altimeter, it is very accurate as long as the air pressure does not change in the area.

A barometer alone is fine for measuring the absolute height above your Take Off location, which your Mavic does all the time when you fly and use the measurement to keep a stable height when your altitude stick is in neutral position.

Greetings Leif.
2017-6-20
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Dennis.D
lvl.2
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Australia
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Have you been able to resolve this issue?  Has the value changed?
What altitude do you take off from?
2017-6-20
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