Some Questions about P4

[RPP]

I am currently in Goa, India, flying my Phantom 4 and it has been a spectacular couple of weeks of photography. I have a few questions and comments:

1) In the metadata for the photos, I see that the altitude is incorrectly recorded. The value recorded seems to be more than the actual altitude - there seems to be a normalizing constant added. (One surprise to me was, Adobe's ACR and Lightroom has the DJI Phantom 4 lens correction profile in their database.)

2) I notice that I get a weak transmission link signal warning when the Phantom is out around 1-1.5 Kms even if I have a direct line of sight. I wonder if I flattened out the antennas (to redirect its radiation pattern) as it got farther away it might make a difference.

3) Yesterday I had a close shave and I should have known about this. I decided to operate into critical battery territory and the bird landed right where it was. Fortunately, it was just 10 metres or so from me and on level ground. If it had happened on missions over water...

4) Finally - I did encounter some sudden rain (vide a thread I started some weeks ago) on a few missions and had to quickly bring home the copter. No issues whatsoever.

I read that I could hold attitude in a critical battery situation but my controller just didn't seem to have any control over once it decided to plonk down.

An example of a photo I took with the Phantom 4.

 

[John Locke]

Regarding the metadata, the craft doesn't know actual elevation to record. It only knows it's launch site as zero elevation. You have to add the launch elevation to get actual elevations from sea level.

Regarding battery after 10%, it will try to land. Full of up ascend with left stick will let you maintain elevation for a little while. It's best to be nearby and land at 20% if you don't want an accident.

The ranges sucks on the P4 controller with a stock antenna. You'll want to upgrade the antenna due to the inherent weaker signal strength of the P4 controller. Or buy an older used Inspire controller like I did.

 

[RPP]

Regarding the metadata, the craft doesn't know actual elevation to record. It only knows it's launch site as zero elevation. You have to add the launch elevation to get actual elevations from sea level.

I have been mostly at sea level myself. The recorded metadata is overstating the altitude. That is, if the copter is flying at, say, 100 metres above sea level, the recorded value says something like 130. Why it is adding a constant is not clear to me.

 

[John Locke]

Oh that issue. Well, I've seen that myself, others have reported it too. It's believed this anomaly was introduced with the firmware update that fixed the yoyo problem. Not sure why this was introduced, but it should have been noticed and resolved during firmware testing, and it wasn't. This seems typical for DJI, releasing firmware that's not well tested. The yoyo problem must have been related to the barometer, and that's obviously also responsible for the current altitude inaccuracy, these two issues are apparently related.

 

[Meta4]

I have been mostly at sea level myself. The recorded metadata is overstating the altitude. That is, if the copter is flying at, say, 100 metres above sea level, the recorded value says something like 130. Why it is adding a constant is not clear to me.

The altitude data problem is that for some unknown and unfathomable reason DJI decided to use GPS for altitude data in the Exif info.
GPS is woefully inaccurate for altitude and it gives (inaccurate) altitude above sea level rather than home point.

 

[John Locke]

My IPad shows wrong altitude data in the GO app too. I will often see a 50' deviation from reality when landing, showing 40 to 55' altitude when it's 5' off the ground. Do you suppose that's GPS generated too?

 

[Meta4]

My IPad shows wrong altitude data in the GO app too. I will often see a 50' deviation from reality when landing, showing 40 to 55' altitude when it's 5' off the ground. Do you suppose that's GPS generated too?

No .. The Phantom doesn't use GPS for flight altitude.
If it did your altitude reading would be up an down all over the place rather than just steady and inaccurate.
Try recalibrating your IMU to see if that makes things any better.

 

[John Locke]

No .. The Phantom doesn't use GPS for flight altitude.
If it did your altitude reading would be up an down all over the place rather than just steady and inaccurate.
Try recalibrating your IMU to see if that makes things any better.

Yeah, good idea. I think I forgot to recalibrate the IMU after the last firmware update, the one that fixed the yoyo.