Phantom 4 keeps loosing height

[rene van der meer]

With a few very specific exceptions*, VPS altitude will be very accurate, and when it's available (lower than 10m/33ft), you can simply ignore the barometric altimeter.

Variation in baro altitude of 20-40 ft over 20 minutes is well within the expected accuracy of this type of altitude measurement.

What's puzzling to me is why the DJI programming doesn't simply ignore the baro sensor when the ultrasonic sensor is available and in range, then switch back smoothly to the baro sensor with a corrected altitude if it ascends again.

....

You are right under 10 m / 30 ft it could use VPS data. It seems the data is only used for x/y positioning (Vision Positioning System) and not z/height.
It also looks like the VPS is not even used as an obstacle avoidance.
This would mean that if the barometric data is off (to high) the quad could even crash into the ground?

 

[dwallersv]

I normally explore complex or hazardous missions first. I use the C1 (waypoint) and C2 keys (POI) to plan the mission. Then I can fly the quad along these stored waypoints. I saw that the position is quite accurate, but the height not and had to abort the mission a few time to prevent the quad hitting the ground.

I've never "recorded" a mission using those features in Litchi before -- gotta give that a try.

I read previously on the forum that Litchi doesn't record altitude when you do this -- was that your experience? It doesn't make sense that it wouldn't...

 

[dwallersv]

You are right under 10 m / 30 ft it could use VPS data. It seems the data is only used for x/y positioning (Vision Positioning System) and not z/height.
It also looks like the VPS is not even used as an obstacle avoidance.
This would mean that if the barometric data is off (to high) the quad could even crash into the ground?

I think you'll probably be okay. There's always risk, but the OA and VPS do a pretty good job of keeping the drone from crashing, especially when it's flying autonomously.

The VPS system also actively monitors and controls the drone for crash avoidance. When VPS sees the drone moving, it will not get closer to the ground than a few feet if flying autonomously. It uses the ultrasonic rangers for precision ranging, ignoring the barometric altimeter. When flying on its own, it simply will not descend to the ground when moving.

Ironically, this is safer than manual control. All the sensors and intelligence of the machine is overridden by user input, so you can slam the thing into the ground at as high a speed as you can attain

Watch this mission run... I love this video. Seems I'm linking it here again and again lately Anyway, this shows just how amazing this technology is, and while nothing's foolproof, after seeing this and then doing some experimentation myself, I'm not too worried about the Phantom plowing the back forty while running a mission close to the ground.

 

[rene van der meer]

I think you'll probably be okay. There's always risk, but the OA and VPS do a pretty good job of keeping the drone from crashing, especially when it's flying autonomously.

The VPS system also actively monitors and controls the drone for crash avoidance. When VPS sees the drone moving, it will not get closer to the ground than a few feet if flying autonomously. It uses the ultrasonic rangers for precision ranging, ignoring the barometric altimeter. When flying on its own, it simply will not descend to the ground when moving.

Ironically, this is safer than manual control. All the sensors and intelligence of the machine is overridden by user input, so you can slam the thing into the ground at as high a speed as you can attain

Watch this mission run... I love this video. Seems I'm linking it here again and again lately Anyway, this shows just how amazing this technology is, and while nothing's foolproof, after seeing this and then doing some experimentation myself, I'm not too worried about the Phantom plowing the back forty while running a mission close to the ground.

That was 9 minutes of my life well spent
Thanks dwallersv!
It surely improved my confidence in the P4.
I just wonder when the VPS obstacle avoidance kicks in. You probably need some horizontal velocity and the height has to be below some point.

 

[dwallersv]

That was 9 minutes of my life well spent
Thanks dwallersv!
It surely improved my confidence in the P4.
I just wonder when the VPS obstacle avoidance kicks in. You probably need some horizontal velocity and the height has to be below some point.

The ultrasonic sensors are always active. Any time they get a solid lock on what it interprets as a surface (remenber the VPS cameras) less than 10m away, it switches to the sonic rangers and ignores the baro altimeter.

If it didn't work this way, a complete RTH would be a disaster most of the time