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GPS weak signal while in flight
283 28 10-3 19:55
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Aramis76
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Hi all,


New Mini 2 here.

I've notice twice now that I get a GPS weak signal after take-off.

I always wait until I have at least 11-12 satellites locked before take-off.

Today, After take-off, I was at 48m altitude when I received the GPS Signal weak message.
At that point, I had 15 satellites locked.

The message only displays for a few seconds and then it's ok.

Last week when I received the Mini 2 (direct from DJI) I updated the Fly app and the firmware so I know everything is up to date.

Is this common?  


This week I will try to go to a different location to take-off, maybe there is some interference around my house?


10-3 19:55
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DJI Stephen
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Hello there Aramis76. I am sorry for the trouble this has caused and thank you for reaching out. Kindly please try to operate and fly your DJI Mini 2 to a different location for us to be able to see if the issue will still persist. Kindly please keep us posted for further assistance. Thank you.
10-3 20:29
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Labroides
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Today, After take-off, I was at 48m altitude when I received the GPS Signal weak message.
At that point, I had 15 satellites locked.
The message only displays for a few seconds and then it's ok.
Is this common?

That's not common or normal.
If the drone is out in the open and clear of any buildings, trees or terrain that could block its skyview, it should always have perfect GPS reception.

I always wait until I have at least 11-12 satellites locked before take-off.
It's inrelated to the issue.
But rather than waiting for some number of sats, you should wait until the drone has recorded a homepoint.
This might require more or less than 11-12 sats.

This week I will try to go to a different location to take-off, maybe there is some interference around my house?
It's unlikely that there's anything nearby that would affect GPS reception.
I've only heard of that being a factor at some locations in Russia and one in Lebanon.

10-3 21:47
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Bashy
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Its not too uncommon as i see this now and again,  the last one  was last weekend and i don't take off until homepoint is recorded
10-3 22:18
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Aramis76
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Both times I have seen this error, it was fine before taking off and the home point had been set before take-off.

Both times when this message appeared, the number of satellites was white and the number of satellites was 15 and 22

Not sure if this makes a difference, but both times this happened, I was in sport mode.

I think it's a software glitch and not an actual GPS problem because when that message appears, the GPS signal is actually good, my altitude is higher than any obstructions.

10-4 04:49
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Labroides
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Aramis76 Posted at 10-4 04:49
Both times I have seen this error, it was fine before taking off and the home point had been set before take-off.

Both times when this message appeared, the number of satellites was white and the number of satellites was 15 and 22

Not sure if this makes a difference, but both times this happened, I was in sport mode.
Sport Mode makes no difference to GPS.

I think it's a software glitch and not an actual GPS problem because when that message appears, the GPS signal is actually good, my altitude is higher than any obstructions.
The way to be sure is to post the flight data.
That will show whether there is a real issue with GPS or not.

10-4 05:18
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Johnny_J
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Aramis76 Posted at 10-4 04:49
Both times I have seen this error, it was fine before taking off and the home point had been set before take-off.

Both times when this message appeared, the number of satellites was white and the number of satellites was 15 and 22

Yes, I've also seen that message when there are no obstructions whatsoever. It seems like the threshold for reporting a weak signal is set too high so the software easily triggers this warning.
DJI will do nothing!
10-4 05:19
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Aramis76
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Labroides Posted at 10-4 05:18
Not sure if this makes a difference, but both times this happened, I was in sport mode.
Sport Mode makes no difference to GPS.

I did export the log, but i'm not sure what to do with this file, it's a 445mb .dat file
10-4 05:21
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Johnny_J
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Aramis76 Posted at 10-4 05:21
I did export the log, but i'm not sure what to do with this file, it's a 445mb .dat file

You can feed the 445 millibits to a log analyzer. Labroides will tell you which one to use.
10-4 05:55
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Labroides
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Aramis76 Posted at 10-4 05:21
I did export the log, but i'm not sure what to do with this file, it's a 445mb .dat file

All that's needed is the .txt file from the app, saved in your phone or tablet.
It's encoded so it won't make sense.

Post it here and I'll check it for you.

10-4 06:10
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Aramis76
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Labroides Posted at 10-4 06:10
All that's needed is the .txt file from the app, saved in your phone or tablet.
It's encoded so it won't make sense.

I get an error when trying to upload the file, something about only accepting pictures.

I was able to upload it to phantomhelp, here is the link, it says something about GPS position mismatch

https://www.phantomhelp.com/LogViewer/SZ4YPSCKNAYONHXB97L2/
10-4 07:23
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Johnny_J
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Aramis76 Posted at 10-4 07:23
I get an error when trying to upload the file, something about only accepting pictures.

I was able to upload it to phantomhelp, here is the link, it says something about GPS position mismatch

When you get an error about an issue that you have a concern about, don't dismiss it as unimportant.
If you cannot understand the message, then save it as a screenshot or as text but NEVER dismiss it!
Then ask the community to help you correctly "decipher" the error and find out what you can do about it.
10-4 07:49
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Aramis76
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Johnny_J Posted at 10-4 07:49
When you get an error that you concern about, don't dismiss it as unimportant.
If you cannot understand the message, then save it as a screenshot or as text but NEVER dismiss it!
Then ask the community to help you correctly "decipher" the error and find out what you can do about it.

That is what i'm doing now, with the link i posted above, you can see my errors.

During flight I can't do a screenshot, it happens too quickly
10-4 07:51
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JJB*
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Aramis76 Posted at 10-4 07:23
I get an error when trying to upload the file, something about only accepting pictures.

I was able to upload it to phantomhelp, here is the link, it says something about GPS position mismatch

Hi Aramis,

Had a look at your log.
See your data in my chart.

At 1m4.1s GPS signal weak, wich sometimes gives a GPS position mismatch too.
Flying full speed in Sport mode, so the position calculation gets 'confused'...

If this happens sometimes and only for short moment, imo noting to worry about.

Windy day, as your gimbal had a tough job to keep steady or was it rapid moves in Sport mode  ;-)

I always fly with a screen recorder active, usefull to replay and analyse each flight for what i ave missed on the screen.

Happy many landings,
cheers
JJB
analysis1.png
10-4 07:52
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Aramis76
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JJB* Posted at 10-4 07:52
Hi Aramis,

Had a look at your log.

Thanks for that!

For the roll limits I think that was me trying to point down to take pictures from above.

But for the wind, it's very possible.

One question, if the compass is not calibrated correctly, can it cause a discrepancy between the GPS reading and the compass?   
10-4 07:58
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JJB*
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Aramis76 Posted at 10-4 07:58
Thanks for that!

For the roll limits I think that was me trying to point down to take pictures from above.

Hi,

GPS and Compass are 2 different systems, they do not conflict each other.
But to hold drone in a stabilized hover, both signals are needed to do so.
(and ofcourse for the whole flight, for automatic corrections to the drone GPS and Compass data is needed)

DJI compasses are calibrated OK on nor OK, if NOK you will see this in the app.

If the compass reading is interfered by metal ect at take-off spot than it can become a error in flight, wich can result in a fly away.

IMO the most important part of the before takeoff checks is to check the compass heading in the map view FlyApp, compare this heading to the actual heading of your drone.
If not the same; DO NOT fly.

Roll limit reached for the gimbal is when yawing the drone rapidly, gimbal cannot follow these movements.
Camera fully down or up is when the gimbal limit is reached.

cheers
JJB
10-4 09:40
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Aramis76
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JJB* Posted at 10-4 09:40
Hi,

GPS and Compass are 2 different systems, they do not conflict each other.

Ok, thanks!  

I was being very quick with motion so that must explain the gimbal limit messages (sport mode).

I read in a few different places that there can be "GPS signal weak" errors when the gps heading and compass reading do not match.   This could explain my problem but I would expect that if that was the case, I would get the error during the entire flight or cause a fly-away as you mention.
10-4 09:44
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GeorgeFoxCinematography
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You don t have every day the same GPS coverage. Check your coverage in your area. Approx 3 months ago and for 3 nights in a row i was not able to fly because i was not able to lock to more than 10 sats and when i was taking off every time i was changing orientation i was loosing a couple ending with as little as 7!(on all my drones including mini 2) I was in an open area. Off course the drone was ok. After checking how many sats were above at that specific time that i was trying to fly, everything came clear. A couple of days later i was able to lock to 20 sats solid.
So try to fly again in a couple of days. Changing area will not do much since to have some effect you will need to travel at least a couple of hours away from where you stood.
10-4 09:54
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Aramis76
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GeorgeFoxCinematography Posted at 10-4 09:54
You don t have every day the same GPS coverage. Check your coverage in your area. Approx 3 months ago and for 3 nights in a row i was not able to fly because i was not able to lock to more than 10 sats and when i was taking off every time i was changing orientation i was loosing a couple ending with as little as 7!(on all my drones including mini 2) I was in an open area. Off course the drone was ok. After checking how many sats were above at that specific time that i was trying to fly, everything came clear. A couple of days later i was able to lock to 20 sats solid.
So try to fly again in a couple of days. Changing area will not do much since to have some effect you will need to travel at least a couple of hour away from where you stood.

Thanks, but as mentioned above, when I get the message, I have between 11 and 21 satellites locked.
10-4 09:57
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Labroides
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Aramis76 Posted at 10-4 07:23
I get an error when trying to upload the file, something about only accepting pictures.

I was able to upload it to phantomhelp, here is the link, it says something about GPS position mismatch

I was able to upload it to phantomhelp, here is the link, it says something about GPS position mismatch
You had two GPS position mismatch errors over a space of three seconds.
During that time the number of sats and the flight controller's assessment of GPS data reliability did not change.
It was a false alarm and never showed up again later in the flight.

One question, if the compass is not calibrated correctly, can it cause a discrepancy between the GPS reading and the compass?
If the compass is not calibrated, you cannot fly properly and would know it.
It wouldn't have any effect on GPS  and can't cause a discrepancy between GPS and compass data, since compass gives direction and GPS gives position.


I read in a few different places that there can be "GPS signal weak" errors when the gps heading and compass reading do not match.   This could explain my problem but I would expect that if that was the case, I would get the error during the entire flight or cause a fly-away as you mention.
What you've read is confusing misinformation.

10-4 15:27
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Labroides
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JJB* Posted at 10-4 07:52
Hi Aramis,

Had a look at your log.

Flying full speed in Sport mode, so the position calculation gets 'confused'...
I'm not sure where you got this idea.
GPS works just fine in jet aircraft flying at 1000 km/hr.
Flying the drone slowly or in Sport Mode makes no difference to GPS.
10-4 15:28
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Aramis76
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Labroides Posted at 10-4 15:27
I was able to upload it to phantomhelp, here is the link, it says something about GPS position mismatch
You had two GPS position mismatch errors over a space of three seconds.
During that time the number of sats and the flight controller's assessment of GPS data reliability did not change.

I too believe it's a false alarm.

I had another flight that received 2 of those weak gps signal warmings about 1 minute between them, but I think that's also a false alarm.

I wonder exactly why that happens and what exactly triggers them.
10-4 15:31
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Labroides
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GeorgeFoxCinematography Posted at 10-4 09:54
You don t have every day the same GPS coverage. Check your coverage in your area. Approx 3 months ago and for 3 nights in a row i was not able to fly because i was not able to lock to more than 10 sats and when i was taking off every time i was changing orientation i was loosing a couple ending with as little as 7!(on all my drones including mini 2) I was in an open area. Off course the drone was ok. After checking how many sats were above at that specific time that i was trying to fly, everything came clear. A couple of days later i was able to lock to 20 sats solid.
So try to fly again in a couple of days. Changing area will not do much since to have some effect you will need to travel at least a couple of hours away from where you stood.

You don t have every day the same GPS coverage. Check your coverage in your area. Approx 3 months ago and for 3 nights in a row i was not able to fly because i was not able to lock to more than 10 sats and when i was taking off every time i was changing orientation i was loosing a couple ending with as little as 7!(on all my drones including mini 2) I was in an open area. Off course the drone was ok. After checking how many sats were above at that specific time that i was trying to fly, everything came clear. A couple of days later i was able to lock to 20 sats solid.
So try to fly again in a couple of days. Changing area will not do much since to have some effect you will need to travel at least a couple of hours away from where you stood.


This is misinformation.
No matter where you are or when, there will always be many more sats available than you need.
GPS is a global, all-weather navigation system.
It's there and working all the time.

If what you said is true and the drone was out in the open with a good skyview, I'd suspect some (rare) GPS interference device was acting near you.

10-4 15:33
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JJB*
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Labroides Posted at 10-4 15:28
Flying full speed in Sport mode, so the position calculation gets 'confused'...
I'm not sure where you got this idea.
GPS works just fine in jet aircraft flying at 1000 km/hr.

True, a good working GPS can handle high speed, no doubt about that.

But when the GPS signal is weak, or the drone thinks that the GPS signal is weak it will not process this data correct. When the drone moves to another postion (more speed gives more distance...), than the new actual position is a different to the one that the drone thinks where it is, as the updating position is not done correctly.
If this happens in flight that the warning GPS postion mismatch is seen, thus a mismatch in actual postion and stored postion.
Happens sometimes flying near buildings ect wich more GPS signal reflection, and/or when the receiving sats are close to each other in the sky.
GPS pos mismatch warning 99% of the time for very short moment, but it is not a false warning made by DJI engineers to confuse us....

This doesn`t happen often, as we are flying most of the time in a open sky envirioment...well i do  ;-)


cheers
JJB

10-4 23:26
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Labroides
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JJB* Posted at 10-4 23:26
True, a good working GPS can handle high speed, no doubt about that.

But when the GPS signal is weak, or the drone thinks that the GPS signal is weak it will not process this data correct. When the drone moves to another postion (more speed gives more distance...), than the new actual position is a different to the one that the drone thinks where it is, as the updating position is not done correctly.

But when the GPS signal is weak, or the drone thinks that the GPS signal is weak it will not process this data correct.
The satellites transmit at a constant power.
If the drone has an unobstructed skyview (like this one did), there's never a weak GPS signal.

When the drone moves to another postion (more speed gives more distance...), than the new actual position is a different to the one that the drone thinks where it is, as the updating position is not done correctly.
If this happens in flight that the warning GPS postion mismatch is seen, thus a mismatch in actual postion and stored postion.
The app would display a speed error if that happened.

Happens sometimes flying near buildings ect wich more GPS signal reflection, and/or when the receiving sats are close to each other in the sky.
GPS pos mismatch warning 99% of the time for very short moment, but it is not a false warning made by DJI engineers to confuse us....
But since it has no effect on the drone flight, it is, in effect a false alarm.
It's something that means nothing and has no detrimental effect and doesn't indicate any real problem..

10-5 01:46
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GeorgeFoxCinematography
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Labroides Posted at 10-4 15:33
You don t have every day the same GPS coverage. Check your coverage in your area. Approx 3 months ago and for 3 nights in a row i was not able to fly because i was not able to lock to more than 10 sats and when i was taking off every time i was changing orientation i was loosing a couple ending with as little as 7!(on all my drones including mini 2) I was in an open area. Off course the drone was ok. After checking how many sats were above at that specific time that i was trying to fly, everything came clear. A couple of days later i was able to lock to 20 sats solid.
So try to fly again in a couple of days. Changing area will not do much since to have some effect you will need to travel at least a couple of hours away from where you stood.


No my friend. Go to NP or SP and do a test. Also GPS is old, all the receivers use as well Galileo and Glonass which are the latest systems. Check with a sat finder to understand what i am saying.
10-5 01:55
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Labroides
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GeorgeFoxCinematography Posted at 10-5 01:55
No my friend. Go to NP or SP and do a test. Also GPS is old, all the receivers use as well Galileo and Glonass which are the latest systems. Check with a sat finder to understand what i am saying.

I don't know what NP or SP is, but you are incorrect.
I've been using GPS professionally for >20 years and flying drones seriously for 6 years.
There's no truth at all in what you are trying to spin.
And a sat finder only confirms that.

10-5 01:59
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JJB*
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Labroides Posted at 10-5 01:46
But when the GPS signal is weak, or the drone thinks that the GPS signal is weak it will not process this data correct.
The satellites transmit at a constant power.
If the drone has an unobstructed skyview (like this one did), there's never a weak GPS signal.

But when the GPS signal is weak, or the drone thinks that the GPS signal is weak it will not process this data correct.
The satellites transmit at a constant power.
If the drone has an unobstructed skyview (like this one did), there's never a weak GPS signal.

True, GPS output by sats is OKE.Bad translation i guess by the DJI engineers, sometimes bad translation by the decrypters...it is a bad quality signal to proces to a good GPS location. That quality is why sometimes HP is set with 8 sats and sometimes set with 11 or 14 sats, just watch the GPS icon turns fropm red>amber>white at different numbers.

When the drone moves to another postion (more speed gives more distance...), than the new actual position is a different to the one that the drone thinks where it is, as the updating position is not done correctly.
If this happens in flight that the warning GPS postion mismatch is seen, thus a mismatch in actual postion and stored postion.
The app would display a speed error if that happened.

Do you know that the decrypters over time uses different self made names for fields and self made text messages ?
The text error "SpeedErrorLarge" was in the GoApp dycrypted csv files, but afaik never seen on the screen as a DJI message.
In the FlyApp csv files all the old GoApp messages like "CompassErrorLarge" and "SpeedErrorLarge" are not seen anymore.

Do you have an screenshot of a speed error message shown from the FlyApp?

Not sure if a GPS position mismatch is never a problem....seen at least 1 log where a GPS position mismatch was the reason for a fly-away to the GPS position where the drone was not at that moment.  But yeah   very very rarely seen so....

cheers
JJB
cheers
JJB




10-5 02:18
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Aramis76
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So i've had a few more flights.  Some show this error, some don't.

At this point, I think it's a software bug, as some have said, it's likely that the threshold for reporting weak signal is not set correctly.

For now, i'll not give these messages any importance as they always occur when the drone has a perfect view of the sky anyway.

It would be nice if DJI could fix this, but it's minor i guess.
10-13 05:49
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