How can I know the AGL altitude of a picture?
- Thread starter lalvar41
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Post the actual image file and I'll find out what I can for you (original file .. the jpg is fine if you have it)
clolsonus
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I believe the DJI phantom 4 (and other models) geotag the altitude with the barometer altitude, not the gps altitude. This has never made any sense for my use cases, but maybe it makes sense for other use cases? Some planning apps will snap a picture on the ground right before launch. Then you can just do the math. Other times I guessed based on how high I told the drone to fly vs. what the approximate ground altitude is at the launch point (using something like SRTM). I'm probably missing something obvious and easy, but those are the sorts of things I have done to work around the issue.
Oh, I believe the DJI mavic 2 pro does geotag the images with the actual gps altitude, so that has been convenient. However, when I hunt through the dji mavic 2 pro flight logs (when flying with the dji go app) no where can I find gps altitude logged. However, when you capture a movie with subtitles turned on, the subtitles include the gps altitude. So all that has been super fun as I've tried to sort through different survey strategies to address some of my own specialized mapping needs.
Oh, I believe the DJI mavic 2 pro does geotag the images with the actual gps altitude, so that has been convenient. However, when I hunt through the dji mavic 2 pro flight logs (when flying with the dji go app) no where can I find gps altitude logged. However, when you capture a movie with subtitles turned on, the subtitles include the gps altitude. So all that has been super fun as I've tried to sort through different survey strategies to address some of my own specialized mapping needs.
There are two altitudes buried in the metadata for that image.
Absolute Altitude: 19.02 metres
Relative Altitude: 76.40 metres
Absolute altitude is DJI's "rough" approximation of altitude above sea level.
But because of the way they calculate it, this is always wrong, sometimes a couple of hundred feet out and the number is useless.
Relative Altitude is the height above launch point as shown on your flying screen.
This should be accurate +/- a couple of metres.
So ... you shot that pic at about 76 metres or 249 feet.
It's in the image metadata.
You just have to know where to look.
clolsonus
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All you said makes a lot of sense. Thank you very much. By the way, which app are you using to get the full metadata details? In Lightroom I don't see all the info you see.There are two altitudes buried in the metadata for that image.
Absolute Altitude: 19.02 metres
Relative Altitude: 76.40 metres
Absolute altitude is DJI's "rough" approximation of altitude above sea level.
But because of the way they calculate it, this is always wrong, sometimes a couple of hundred feet out and the number is useless.
Relative Altitude is the height above launch point as shown on your flying screen.
This should be accurate +/- a couple of metres.
So ... you shot that pic at about 76 metres or 249 feet.
It's in the image metadata.
You just have to know where to look.
That was Picture Information Extractor (and that was only part of the information)
The ultimate tool for digital cameras reveals everything. Picture Information Extractor
www.picmeta.com
Picture Information Extractor - EXIF IPTC | Picmeta Systems
EXIF/IPTC Toolkit with File Rename, Capture Date/Time Change, Lossless Rotation, Transfer. All RAW formats supported.
Earthman
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Another tip for when you have a good horizon in the background.
The line between your eye and the horizon while flying in a plane (or the drone’s camera in this case) is a level line.
So, any object above the horizon is above you and any object below the horizon (like the top of the building in your photo) is below you.
Good to know if you are a private, drone, or fighter pilot. Ignoring today’s advanced weapons, in general, fighter pilots have more options and the advantage when they are above their opponent(s).
Assuming a commercial building’s floors are 10’ to 12’ high, you can use the building in the photo as a scale to estimate the height of the drone.
The line between your eye and the horizon while flying in a plane (or the drone’s camera in this case) is a level line.
So, any object above the horizon is above you and any object below the horizon (like the top of the building in your photo) is below you.
Good to know if you are a private, drone, or fighter pilot. Ignoring today’s advanced weapons, in general, fighter pilots have more options and the advantage when they are above their opponent(s).
Assuming a commercial building’s floors are 10’ to 12’ high, you can use the building in the photo as a scale to estimate the height of the drone.
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clolsonus
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After a sad/unexpected experience last spring, I now burn the first part of my first battery launching and climbing and looking around at the horizon until there are no tree tops extending above the horizon. Then I can note that altitude as my minimum safe survey altitude for the area.
R.Perry
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Well I came up with closer to 280 to 300 feet AGL, you have a twenty four story building and you are slightly above it.
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