Photo altitude?

[Meta4]

In my place we are around 3200 masl (Metres Above Sea Level). When I saw the altitude in EXIF data it was only +35m, not 3250m. Is there any way to fix this?

There's no way to change the way your drone is setting exif data.

I was reading more about this, and there are some others with the same issue than me.
In all my pictures taken shows: (well I tried at 35m) (in all pictures doesn't change absolute altitude)
Absolute Altitude : +1.20
Relative Altitude : +35.00

Those numbers seem unlikely if you were flying from 3000 metres above sea level.
In Exif info the absolute altitude is only an approximate number but it should be roughly equivalent to the drone's ASL altitude (but it can be a few hundred feet out)
The relative altitude should be the drone's height relative to the launch point.

 

[AnglSalvatierra]

There's no way to change the way your drone is setting exif data.


Those numbers seem unlikely if you were flying from 3000 metres above sea level.
In Exif info the absolute altitude is only an approximate number but it should be roughly equivalent to the drone's ASL altitude (but it can be a few hundred feet out)
The relative altitude should be the drone's height relative to the launch point.

So something is wrong. I was reading there are some problems with that information.

 

[Meta4]

So something is wrong. I was reading there are some problems with that information./QUOTE]
I suggested that it's unlikely that the numbers you posted would come from a photo shot at 3000 metres ASL.
The inaccuracy I'd expect might be approx 60 metres in the absolute altitude
I doubt your camera is giving numbers with an error of 3000 metres.
Post an original image file and I can check.

 

[AnglSalvatierra]

I don't know whats wrong. Well my drone it's not a mavic pro, it's a mavic air.

 

[Meta4]

I don't know whats wrong. Well my drone it's not a mavic pro, it's a mavic air.

There is something unusual in the way your camera is recording altitude data
For that image it gives:

AbsoluteAltitude +1.20​

RelativeAltitude +35.00​

Where it's getting 1.2 metres for Absolute Altitude is a puzzle.
DroneDeploy list the Mavic Air as a supported drone so it's logical that the exif info should be similar to the way other DJI drones record exif.
I compared exif info from your image with data from a Phantom 4 image:

There are two things that stand out.
1. Why does it record 1.2 metres as Absolute Altitude? (should be >3000m)
2. Why is it picking up Relative Altitude and showing that as height ASL? (should be using Absolute Alt).

Perhaps @sar104 can make sense of this puzzle?

 

[AnglSalvatierra]

There is something unusual in the way your camera is recording altitude data
For that image it gives:

AbsoluteAltitude +1.20​

RelativeAltitude +35.00​

Where it's getting 1.2 metres for Absolute Altitude is a puzzle.
DroneDeploy list the Mavic Air as a supported drone so it's logical that the exif info should be similar to the way other DJI drones record exif.
I compared exif info from your image with data from a Phantom 4 image:

There are two things that stand out.
1. Why does it record 1.2 metres as Absolute Altitude? (should be >3000m)
2. Why is it picking up Relative Altitude and showing that as height ASL? (should be using Absolute Alt).

Perhaps @sar104 can make sense of this puzzle?

Well picture was taken with Pix4Dcapture. I really don't know why AbsoluteAltitude is at +1.20, RelativeAltitude +35.00 is set in the app. Maybe a firmware problem. In DJI forum I found this:

mavic pro 2 exif GPS Altitude not working...

Greetings DJI While shooting jpeg or DNG results in the photo is being tagged with a funky GPS Altitude. Here's what exiftools says (which matches photoscan): GPS Altitude : 115161993.7 m Above Sea Level thanks!

forum.dji.com

 

[Meta4]

Well picture was taken with Pix4Dcapture. I really don't know why AbsoluteAltitude is at +1.20, RelativeAltitude +35.00 is set in the app. Maybe a firmware problem.

Have you tried to get altitudes or contours from Pix4D?
If so, what altitudes did it show?

Using Pix4D should make no difference, the camera data should be the same whatever app you fly with.
It might be useful to see an image from someone else's Mavic Air to compare.

 

[AnglSalvatierra]

Have you tried to get altitudes or contours from Pix4D?
If so, what altitudes did it show?

Using Pix4D should make no difference, the camera data should be the same whatever app you fly with.
It might be useful to see an image from someone else's Mavic Air to compare.

Yeah, I tried to set my altitude, but there isn't option. It only shows the altitude I set to fly drone.

 

[Meta4]

Yeah, I tried to set my altitude, but there isn't option. It only shows the altitude I set to fly drone.

There's nothing you can set that affects exif info.
It records exactly the same way that it's programmed to by camera firmware.

 

[sar104]

There is something unusual in the way your camera is recording altitude data
For that image it gives:

AbsoluteAltitude +1.20​

RelativeAltitude +35.00​

Where it's getting 1.2 metres for Absolute Altitude is a puzzle.
DroneDeploy list the Mavic Air as a supported drone so it's logical that the exif info should be similar to the way other DJI drones record exif.
I compared exif info from your image with data from a Phantom 4 image:

There are two things that stand out.
1. Why does it record 1.2 metres as Absolute Altitude? (should be >3000m)
2. Why is it picking up Relative Altitude and showing that as height ASL? (should be using Absolute Alt).

Perhaps @sar104 can make sense of this puzzle?

There was a previous firmware version for the MP that recorded all altitudes as +1.2 m. It was fixed later on. That may be the problem here.

@Lightsped - which firmware version are you on?

 

[AnglSalvatierra]

There was a previous firmware version for the MP that recorded all altitudes as +1.2 m. It was fixed later on. That may be the problem here.

@Lightsped - which firmware version are you on?

Well, I've looked for updates, but there ins't anything new yet.

 

[ardash@adelaide]

So there indeed is a field called "Altitude" in the EXIF data, and I've always assumed it's from the drone itself via GPS, along with the coordinates (i.e. absolute height from sea level). And at least in Lightroom it's reported as meters, with the unit.

However, now that I took a closer look at some of the recorded altitude values, they seem to be all over the place. I have several photos showing negative altitude in double digit meters – while literally flying above sea. And in many other cases the values don't seem to correspond to the height I'm able to eyeball from the photos. Not sure if there's just something wrong in my particular unit regarding the EXIF-recorded height or is this a common behaviour. In any case the altitude shown during flight and what is in the flight logs seem to be pretty much spot-on correct, so with some manual labor you should be able to get the actual heigth for any photo. Really wish the EXIF data was correct too though…

Yes I have same issues with the new Mini 3 Pro. My photos have metadata in the Exif GPS group and are shown in the Altitude field of Lightroom metadata view. But they are all negative (for photos taken with the drone). See extract from exif data using exiftool program:

[GPS] GPSAltitudeRef : Below Sea Level
[GPS] GPSAltitude : 34.174 m

 

[Meta4]

Yes I have same issues with the new Mini 3 Pro. My photos have metadata in the Exif GPS group and are shown in the Altitude field of Lightroom metadata view. But they are all negative (for photos taken with the drone). See extract from exif data using exiftool program:

[GPS] GPSAltitudeRef : Below Sea Level
[GPS] GPSAltitude : 34.174 m

If you could see all the Metadata (many viewers just show part of it), you would see two different altitude numbers.
Relative Height = the height you see on your screen while flying.
Absolute height = an inaccurate approximation of height relative to sea level, derived from atmospheric pressure with a poor formula.
Despite DJI labelling this as GPS altitude, it does not come from GPS.
I'm pretty sure that the drone wasn't 67 metres below sea level for this shot.

 

[Meta4]

Yes I have same issues with the new Mini 3 Pro.

Post one of your full-size original jpgs and I'll show you what the Metadata really shows.

 

[ardash@adelaide]

If you could see all the Metadata (many viewers just show part of it), you would see two different altitude numbers.
Relative Height = the height you see on your screen while flying.
Absolute height = an inaccurate approximation of height relative to sea level, derived from atmospheric pressure with a poor formula.
Despite DJI labelling this as GPS altitude, it does not come from GPS.
I'm pretty sure that the drone wasn't 67 metres below sea level for this shot.

Yes I see all that data - I just don't get why my photo reports being taken at -34 meters when it was taken at +25 meters above ground take off. Here is all metadata with"altitude" in the word:

[GPS] GPSAltitudeRef : Below Sea Level

[GPS] GPSAltitude : 34.174 m

[XMP-drone-dji] AltitudeType : RtkAlt

[XMP-drone-dji] AbsoluteAltitude : -34.174

[XMP-drone-dji] RelativeAltitude : +25.700

[Composite] GPSAltitude : 34.1 m Below Sea Level

 

[Meta4]

Yes I see all that data - I just don't get why my photo reports being taken at -34 meters when it was taken at +25 meters:

It's because DJI was sloppy and uses a flawed formula to derive altitude above sea level from air pressure.
It assumes that air pressure is constant and ignores the fact that it goes up and down.
Try some stest shots from the same place on days with different air pressure and see how they vary to indicate above and below sealevel.

Then to make it ever sloppier, they label it GPS altitude.

 

[ardash@adelaide]

It's because DJI was sloppy and uses a flawed formula to derive altitude above sea level from air pressure.
It assumes that air pressure is constant and ignores the fact that it goes up and down.
Try some stest shots from the same place on days with different air pressure and see how they vary to indicate above and below sealevel.

Then to make it ever sloppier, they label it GPS altitude.

Yeah thanks - I suspected the -34 was incorrect but that's 50 meters off the correct mark. Hard to imagine air pressure would do that much. But I will do more tests and report back.

 

[Meta4]

Yeah thanks - I suspected the -34 was incorrect but that's 50 meters off the correct mark. Hard to imagine air pressure would do that much. But I will do more tests and report back.

The absolute altitude number is useless and best ignored.
If you really need to calculate the drone's height above sea level when a particular photo was taken, you'd have to go back and work it out yourself from the relative height and the altitude of your launch point.

 

[Meta4]

Yeah thanks - I suspected the -34 was incorrect but that's 50 meters off the correct mark. Hard to imagine air pressure would do that much. But I will do more tests and report back.

Or ... I notice that metadata from the M3 shows some differences to metadata from earlier drones I used.
For one shot with the M3, it shows:
Absolute Altitude: -51.122
Altitude Type: GpsFusionAlt

They used air pressure in earlier models (discovered by Sar104).
But perhaps they are using GPS now which could give incorrect results due to problems with the geoid not properly representing the actual shape of the earth ?

 

[ardash@adelaide]

Or ... I notice that metadata from the M3 shows some differences to metadata from earlier drones I used.
For one shot with the M3, it shows:
Absolute Altitude: -51.122
Altitude Type: GpsFusionAlt

They used air pressure in earlier models (discovered by Sar104).
But perhaps they are using GPS now which could give incorrect results due to problems with the geoid not properly representing the actual shape of the earth ?

My Altitude Type is RtkAlt - don't know what that means although RTK is "real time kinematics" used in the enterprise drone space.