Max Alt issue?

[Transition]

Hi folks, yesterday, after getting FAA clearance to fly in 0 grid in D airspace a mile east of an airport up 150ft, I set my max altitude to 147ft. On my first flight I noticed I was at 184ft for a moment, and descended straight away. When I got home I looked at my flight log on my Tripletek tablet and it showed 56 meters (183.73ft). Usually I get a warning say “you have reached your max altitude”. I checked in my setting and my Max Alt was still showing 147ft. Has anybody else had this issue, or did I just miss something here??

Thank you for your input!

Mark

 

[Meta4]

my flight log on my Tripletek tablet and it showed 56 meters (183.73ft). Usually I get a warning say “you have reached your max altitude”. I checked in my setting and my Max Alt was still showing 147ft.

Post your recorded flight data and it might help to explain what happened.

 

[Transition]

Thanks for your reply. Sorry if I may sound dumb, but how do I do that?

Thanks again!
Mark

 

[Starz]

This site does have a search feature. It works pretty well.
This is what I found.

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

 

[Transition]

Thank you…I’ll try that!

 

[Farkyard]

I yesterday discovered one of my Enterprise Duals was doing this. Wondering if you got anywhere with the issue?

 

[AlanL]

Make sure that the number you are reading in your logs is referencing elevation above your launch point. I noticed that the EXIF data for my M3 is recording elevation above sea level even though everything on my screen during flight is AGL.

 

[Farkyard]

Make sure that the number you are reading in your logs is referencing elevation above your launch point. I noticed that the EXIF data for my M3 is recording elevation above sea level even though everything on my screen during flight is AGL.

Mate I am pretty much flying from sea level where I was so shouldn't be a difference. Only one I have ever had that is doing this to my knowledge. Going to have check the others now to see if they are also doing it.

 

[AlanL]

Mate I am pretty much flying from sea level where I was so shouldn't be a difference. Only one I have ever had that is doing this to my knowledge. Going to have check the others now to see if they are also doing it.

Yeah - and the OP is in Florida according to his sig so not much different than your situation.

I am used to the same scenario flying around my area but was surprised that DJI was in fact recording elevation above mean sea level when I was flying up in the Columbia River Gorge. I was shooting from 100' above ground level near some cliffs but the Columbia River was 700' below my launch point. The images have EXIF data showing that I was at 821' MSL. It would be nice if we had full access to what all they really are logging as info.

 

[Farkyard]

I

Yeah - and the OP is in Florida according to his sig so not much different than your situation.

I am used to the same scenario flying around my area but was surprised that DJI was in fact recording elevation above mean sea level when I was flying up in the Columbia River Gorge. I was shooting from 100' above ground level near some cliffs but the Columbia River was 700' below my launch point. The images have EXIF data showing that I was at 821' MSL. It would be nice if we had full access to what all they really are logging as info.

Its interesting. Judging by a search I'm obviously not the first and unlikely to be the last!

 

[Meta4]

I ... was surprised that DJI was in fact recording elevation above mean sea level ... The images have EXIF data showing that I was at 821' MSL. It would be nice if we had full access to what all they really are logging as info.

Your image metadata has two different heights.
One is the height you see on your screen and one is (a very rough approximation of) height above sea level.
Post one of your full original jpg files and I'll show you the two different heights in the metadata.

 

[AlanL]

Your image metadata has two different heights.
One is the height you see on your screen and one is (a very rough approximation of) height above sea level.
Post one of your full original jpg files and I'll show you the two different heights in the metadata.

I just posted one of the shots in question in the Photos Forum. Yes both height measures are visible in the raw metadata but not in the usual EXIF displayed data.:

<drone-dji:AbsoluteAltitude>+204.545</drone-dji:AbsoluteAltitude>
<drone-dji:RelativeAltitude>+81.500</drone-dji:RelativeAltitude>

I'd love to be able to see the Absolute Altitude on my display when I am flying.

 

[Meta4]

I'd love to be able to see the Absolute Altitude on my display when I am flying.

Perhaps not if you knew how inaccurate and usless the Absolute Altitude numbers really are.
Here are a couple of examples.
btw .. although DJI label it GPS altitude, it does not come from GPS.

 

[Elthree]

The metadata does have two altitude values:
Relative (above the Home Point), and
Absolute (above the GPS Datum).

This is GPS basics, and nothing to do with drones specifically. It's not that the GPS altitude is "wrong" somehow.

It's NOT "above sea level". The GPS Datum is a "zero level" on a modelled ellipsoid/spheroid that approximates the shape of the earth. Different map systems have different datums, and if you're dealing with geolocation systems in any precision you need to know the differences.

Apart from anything else, the tides go up and down but the GPS zero altitude doesn't. And how much it differs from the "mean sea level" varies across the globe.

Some way of having the drone know/show "AGL" would be great, as that's what we (and the authorities) usually care about. But unfortunately life just isn't that simple.

 

[Meta4]

This is GPS basics, and nothing to do with drones specifically. It's not that the GPS altitude is "wrong" somehow.

Actually, it is that the "GPS Altitude" is wrong as I demonstrated in the previous post.
It is nominally above (or below) sea level, but despite DJI's misleading name, doesn't come from GPS.
It comes from a conversion using a flawed formula based on atmospheric pressure, but it doesn't account for variation in air pressure.

 

[Elthree]

How did you demonstrate it?
Where those two photos taken in similar locations? There was nothing to suggest they were.

 

[Meta4]

How did you demonstrate it?
Where those two photos taken in similar locations? There was nothing to suggest they were.

Yes ... shot fairly close to the same spot a couple of months apart.
I've posted them before and explained it that time.
I saw the pix and assumed it was the post that explained it.