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Why am I seeing -22.3 feet when the drone is at about 5 feet altitude?

Dronenewbie8

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Hello. I have a Mavic 2 Pro. When I flew today I had problems with the Flight Telemetry info in the GO4 App.001_before take off, RC is 18 feet from drone, D says 5.8 feet, HomePoint says 76.3 feet.jpg002_approx 25 feet altitude, H says 5.6 feet.jpg003_approx 5 feet altitude, H says -22.3 feet.jpg

I manually set the home point, the drone was sitting on the helipad, I was standing 18 feet away holding the RC. As shown in the first screenshot, D says 5.8 feet, and the Home Point icon says 76.3 feet.

Second screenshot. The drone was at approx. 25 feet altitude yet H says 5.6 feet.

Third screenshot: The drone was at approx. 5 feet altitude yet H says -22.3 feet.

I had similar issues when I took off automatically.

Also, when I set the Home point manually, about half the time I hear the voice “Home point has been set, please check it on the map” and half the time there isn’t any voice.

Can anyone offer any suggestions and/or advice as to what’s going on?

Thanks.
 
Before anyone answers, can you turn off the overexposure setting. It's making my eyes bleed
 
Second screenshot. The drone was at approx. 25 feet altitude yet H says 5.6 feet.
Third screenshot: The drone was at approx. 5 feet altitude yet H says -22.3 feet.
I can't tell from what you've posted ...
Was the drone 5 feet higher than where it started and 22 feet lower than where it started?

Your screen shots suggest:
#2 the drone is 26 ft above the ground and 5 ft higher than where it started
#3 the drone is 4 ft above the ground and 22 ft lower than where it started

Also, when I set the Home point manually, about half the time I hear the voice “Home point has been set, please check it on the map” and half the time there isn’t any voice.
That's not unusual.
Sometimes you'll hear it, sometimes not.
 
Also, when I set the Home point manually, about half the time I hear the voice “Home point has been set, please check it on the map” and half the time there isn’t any voice.

Are you sure you've always got the volume turned up on your phone / tablet?
 
Are you sure you've always got the volume turned up on your phone / tablet?

I don't tweak the volume settings. During the same flying session sometimes it's there, sometimes it isn't. It happened to day as well. When I set the Home Point manually I don't hear it; if I use Auto Takeoff I hear it.
 
I can't tell from what you've posted ...
Was the drone 5 feet higher than where it started and 22 feet lower than where it started?

Your screen shots suggest:
#2 the drone is 26 ft above the ground and 5 ft higher than where it started
#3 the drone is 4 ft above the ground and 22 ft lower than where it started


That's not unusual.
Sometimes you'll hear it, sometimes not.

Thanks for your replies. The field I flew in was previously built up, then razed, and flattened out. There were certain areas in this field that I couldn't take off due to MAG INTERFER. I moved 100 feet and could launch. I think the problem with this particular field is that there's a lot of metal underground that's messing up the telemetry info. Today I flew at a different field and no problems at all.
 
I think the problem with this particular field is that there's a lot of metal underground that's messing up the telemetry info.
Magnetic interference can only have an effect on the compass.
It won't have any effect on the altitude sensors at all.

Do you have any comments on the questions from post #3?
 
I can't tell from what you've posted ...
Was the drone 5 feet higher than where it started and 22 feet lower than where it started?

Your screen shots suggest:
#2 the drone is 26 ft above the ground and 5 ft higher than where it started
#3 the drone is 4 ft above the ground and 22 ft lower than where it started


That's not unusual.
Sometimes you'll hear it, sometimes not.

Hi again and thanks for your reply. I wasn't aware that Mag Interference affects the compass only - good to know.

Regarding the screenshots, I set the home point while the drone was on the helipad, before take-off. (In screenshot #1 why is "D" 5.8 feet when the drone is on the helipad and hasn't moved an inch? And I'm not sure why the symbol with the man and home point indicates 76.3 feet when the drone is still on the helipad and I'm 18 feet away, holding the RC)

I took off and let the drone hover at around 20 feet for a few seconds, then went flying. So....do you think perhaps a new home point altitude was recorded while the drone was hovering at around 20 feet? If that's the case then your comments would make sense.
 
I set the home point while the drone was on the helipad, before take-off. (In screenshot #1 why is "D" 5.8 feet when the drone is on the helipad and hasn't moved an inch?
The drone sets its home point automatically when it first gets good GPS location data.
Did you reset the home point after that?
D=5.8ft means the drone is 5.8 ft away from the home point
Had the drone been moved after the home point was set?
If not, the recorded flight data might help explain.
And I'm not sure why the symbol with the man and home point indicates 76.3 feet when the drone is still on the helipad and I'm 18 feet away, holding the RC)
The 76.3 ft means that the drone is 76.3 ft away from the controller.
I took off and let the drone hover at around 20 feet for a few seconds, then went flying. So....do you think perhaps a new home point altitude was recorded while the drone was hovering at around 20 feet? If that's the case then your comments would make sense.
New home points don't get recorded if you already have good GPS.
There is no altitude recorded for a home point, just a lat and long.

I'm not understanding clearly what the situation is with your drone.
Some of what you've said is confusing.
 
The drone sets its home point automatically when it first gets good GPS location data.
Did you reset the home point after that?
D=5.8ft means the drone is 5.8 ft away from the home point
Had the drone been moved after the home point was set?
If not, the recorded flight data might help explain.

The 76.3 ft means that the drone is 76.3 ft away from the controller.

New home points don't get recorded if you already have good GPS.
There is no altitude recorded for a home point, just a lat and long.

I'm not understanding clearly what the situation is with your drone.
Some of what you've said is confusing.

Thanks again for your replies, I appreciate the time you've put into looking into this.

One thing that's confusing is that when I was 18 feet from the recorded home point, holding the controller, the "D" read 5.8 feet (not metres) and the distance from the controller read 76.3 feet; these readings were while my drone was sitting on the helipad, before take-off. The drone hadn't been moved even an inch after the home point was recorded.

I'll go back to the same area in that same field and try all of this again, see what happens.
 
For me the altitude accuracy can be very poor sometimes. GPS is rather inaccurate when it comes to altitude. Many times after I fly for a while and then return to my same launch location it will read a minus altitude. Sometimes as much as 5 meters. So what I do sometimes if I need accurate altitude information, i fly for several minutes, land the drone back home briefly ( often apparently lower than where I took off from even though it’s the same spot), and then take off again. After being in the air the drone seems to get better gps readings and things are more accurate. The reason I noticed this behavior is because I’ve flown the same waypoint mission several times during several flights, and have gotten different results due varying altitude during the flights. Definitely don’t trust the altitude when planning waypoint missions. It could easily crash you into a building or tree.
 
After being in the air the drone seems to get better gps readings and things are more accurate.
GPS is as accurate at the start of your flight as it is later.
But your drone gets altitude data from its barometer, not GPS.
It's common to see a small change due to warming up during a flight.
 
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