DJI Phantom Vision 2 - bad height readings

A

ALMPilot

Member
My DJI Phantom Vision 2 is giving me some bad reading for the height. The compass calibration was really messed up when I got the quadcopter.

I am at sea level and and the height reading on the iPhone app will tell me that the height is -3m at ground level. The last few flights I have seen -8m about 18m off the ground. I am new to quadcopters, this is my first. Does anyone know what I can do to fix this?
 

Benjamin Kenobi

Benjamin Kenobi

Easy? You call that easy?
Re-calibrate the compass. I believe the height readings come from GPS. Do you have full GPS lock before taking off? (ie no red lights) GPS is only accurate to within a few meters also so expect some deviation. Does it record the home position correctly when taking off (flashing green light I think)? The height is based on the distance from the home position. Are there buildings or structures nearby?

A height reading of -8m at 18m altitude does seem incorrect. How many times did it give these readings?

Again, recalibrate the compass and see if that helps.
 

T

Tahoe Ed

Active Member
I have had some readings that were not completely accurate but when I tested RTH, it landed perfectly. The altitude is more than the GPS it is also the Baro in the Naza. If I am flying at 150m, +/- 10m is not that big of a deal for me. I would do the Advanced Calibration of the IMU and recalibrate the compass when you get ready to fly. Other than that I would look at the altitude as a relative figure +/- 10%.
 
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A

ALMPilot

Member
Benjamin Kenobi said:
Re-calibrate the compass. I believe the height readings come from GPS. Do you have full GPS lock before taking off? (ie no red lights) GPS is only accurate to within a few meters also so expect some deviation. Does it record the home position correctly when taking off (flashing green light I think)? The height is based on the distance from the home position. Are there buildings or structures nearby?

A height reading of -8m at 18m altitude does seem incorrect. How many times did it give these readings?

Again, recalibrate the compass and see if that helps.
Click to expand...


Sometimes I have the GPS lock before take off but not always. I think I have gotten flashing green or was it solid green? I will have to check that back. There are some buildings nearby. I will retry the calibration tonight. When I first got it out of the box the compass was very messed up, the app kept telling me that calibration was needed.

Can anyone post the expected compass readings from the DJI software? I will try to post my own when I do the calibration.
 

A

ALMPilot

Member
Tahoe Ed said:
I have had some readings that were not completely accurate but when I tested RTH, it landed perfectly. The altitude is more than the GPS it is also the Baro in the Naza. If I am flying at 150m, +/- 10m is not that big of a deal for me. I would do the Advanced Calibration of the IMU and recalibrate the compass when you get ready to fly. Other than that I would look at the altitude as a relative figure +/- 10%.
Click to expand...

Ed,

10m offset sounds like quite a lot. I did the advanced calibration initially but I am trying again tonight. It's telling me it is too hot for the calibration and that I have to turn it off and wait for it to cool down.

In the meantime, my raw compass reading values are:

x = 50, y = -165, z = 42, mod = 2041 is this bad, can you say? I was looking at this video and I am thinking there could be an issue: http://www.youtube.com/watch?v=Vo7Kf3uo93I
 

T

Tahoe Ed

Active Member
Your compass has nothing to do with the altitude readings. It is a combination of the Barometer sensor reading and the GPS. You may have a bad baro. It is more sensitive to altitude changes than the GPS is. That is why I recommended doing the Advanced Calibration.
 

A

ALMPilot

Member
Well I was expecting some offset with height but I think this is too much.

I did the advanced calibration and the offset then was -2.1m. I thought that was fine no problem I can work with that but when I took it outside I got the GPS lock (blinking green LEDs, 7-8 satellites) it held the value. I did the compass calibration outside and then the readings went back to being -8m at about 1 to 2m off the ground. I am at sea level, what's going on?


It's about time I write my product review for this thing.
 

T

Tahoe Ed

Active Member
Have you contacted your Dealer about this? If it is a bad Baro sensor, swapping the Naza V2 would be an easy fix. See what they say.
 

A

ALMPilot

Member
I did the compass calibration a couple times and the offset went to around 2m. Had several good long flights and it was great.


Today I went to take a flight and the compass needed calibration. I couldn't get the calibration to work. I hooked it up to the pc and the raw compass mod value was awful:


x 215 y -72 and z -83 mod 22845


I tried using a magnet to fix it like in the youtube video with Colin Guinn but very little happened.


I also did the basic and advanced calibrations with no effect. I am so frustrated and annoyed right now. I will try calling the dealer tomorrow.


Anyone has any ideas about what I can try to fix this?
 


A

ALMPilot

Member
well that is pretty cool nisouck how did you get the video so stable? The phantom 2 vision is a bit jittery. I jiggles a bit.


Anyway I shipped my vision back to the dealer yesterday. The compass went totally haywire and once that happened there was no GPS lock or satellite detection.


I am pretty disappointed, I don't see why a new and supposedly premium quality product should be doing something like this.
 


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