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Altitude wrong in video caption
253 12 9-19 05:32
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marklyn59
First Officer
Flight distance : 395072 ft
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Playing around with the video caption and so far, the altitude seems to be wrong on every flight. My area's height above sea level is generally around 700'.
When I take off from anywhere in my immediate area the altitude on the video caption shows around 240' (give or take a few feet depending on what street I'm on in my hood).
The altitude display on the DJI Go app and console is correct.  Why is the altitude recorded in the caption file so blatently off (usually around 150-175').  I've done about 8 flights and all altitudes in the produced caption files are like this.

The snapshot below is a good example.  Altitude show around 240' yet I'm no more than 15-20' off the ground.








altitude.PNG
9-19 05:32
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DAFlys
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Flight distance : 410256 ft
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Prepare for the standard DJI response.
9-19 05:45
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JJB*
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Flight distance : 1144157 ft
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Hi,

Interesting question, do you know of your baro press that day was about 1005 mbar ??

cheers
JJB

9-19 06:04
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marklyn59
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Flight distance : 395072 ft
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JJB* Posted at 9-19 06:04
Hi,

Interesting question, do you know of your baro press that day was about 1005 mbar ??

No, I don't... why?
9-19 10:10
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JJB*
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marklyn59 Posted at 9-19 10:10
No, I don't... why?

If DJI uses the standard barometer setting as reference ; reference is at sea level 1013 mbar - 15 degrees C.

For every 30 feet plus height the pressure drops with 1 mbar.
So indicating 240 ft = 240 / 30 = 8 mbar.
2013 - 8 = 2005 mbar.

Temperature have some effect as well, did not calculate that.
After take-off the baro height is reset to zero, that`s why in the app you will see values wich represent the actual heigt above take off point.

BTW not 100% sure if it works like this, have to go into the files as the height before zero-ing is written as well.
cheers
JJB
9-19 11:00
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Ex Machina
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Flight distance : 1418406 ft
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In case you haven't seen this: mavic pro 2 exif GPS Altitude not working...
9-19 13:05
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gnirtS
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Flight distance : 2993497 ft
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Maybe a coincidence but 700ft is about 240m.  
Maybe its recording in metre and just saying "feet" after it?
9-19 13:23
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marklyn59
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Flight distance : 395072 ft
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gnirtS Posted at 9-19 13:23
Maybe a coincidence but 700ft is about 240m.  
Maybe its recording in metre and just saying "feet" after it?

If it's in meters then translating over to feet would make sense but of course there isn't any indication of whether this is supposed to be feet or meters.
Wish DJI would jump in and comment.
9-19 18:56
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marklyn59
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Flight distance : 395072 ft
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Ex Machina Posted at 9-19 13:05
In case you haven't seen this: mavic pro 2 exif GPS Altitude not working...

long thread but the gist of it seems to be there isn't an acknowledged fix, or at least that what I'm reading between all of the useless bickering.
9-19 19:06
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gnirtS
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marklyn59 Posted at 9-19 18:56
If it's in meters then translating over to feet would make sense but of course there isn't any indication of whether this is supposed to be feet or meters.
Wish DJI would jump in and comment.

Relatively easy to test.  Just do some flights and take video at different,known altitudes and see if the trend continues.
9-19 19:29
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Ex Machina
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marklyn59 Posted at 9-19 19:06
long thread but the gist of it seems to be there isn't an acknowledged fix, or at least that what I'm reading between all of the useless bickering.

It'll take a firmware fix. Not sure if you are getting GPS altitude or Barometric altitude in video captions, though, so...
9-20 05:29
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marklyn59
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Flight distance : 395072 ft
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Any ideas on the best way to get DJI's attention on this? Do  I "open a case" with them or just hope that one of the DJI moderators will eventually see this and act on it?
9-20 13:21
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Ex Machina
Captain
Flight distance : 1418406 ft
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marklyn59 Posted at 9-20 13:21
Any ideas on the best way to get DJI's attention on this? Do  I "open a case" with them or just hope that one of the DJI moderators will eventually see this and act on it?

It's best to open a case, but you can also enter a bug report -- both are done via Go 4's Me section. If an admin here sees it and also forwards it on, all the better.
9-20 14:50
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