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Dji mavic mini gps problems

Geri87

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Hello.This is my first post and this is my second mavic mini fcc version.Ordered on amazon.The drone seems to have extreme difficoulties in finding gps sats.It starts normal in an open space and then as soon as reaches some altitude over 50m gps looses signal and give sensor error.I have calibrated it normally.I have tried many locations by now but they are all in the city, although i have never had gps problems with my old mavic mini in the city which i crashed acciddentaly,i mean i could start it inside my 8-th floor apartment and then as soon as it got out it would find the gps but this new one does not.The product has been activated with dji refresh but i dont know if i should do more tests,return it back to the seller or just return to dji since i have the refresh care.Any opinion would be appreciated.Thanks
 

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Geri87

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I have updated the drone firmware from dji assistent 2 the only thing left is to go to an open field try to calibrate and see if its a fixable solution.Its really frustrating considering the mini is by far one of the best choices on the market.
 

Geri87

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I tried another place still in the city.Same thing it keeps messing with the gps lock 11,12 then drops to 7,6,4,0 i cannot go over 20 meters certain time and other times i cannot go over 50 meters in altitude and if if i move horizonatly still messes with the gps it moves a lot.I saw my flight log its crazy it can start barelly 10,11 and then as soon as i take off a little altitude it drops to 0 then of course goes to attitude mode(very dangerous).Never got more than 4 white bars.I send a request to the support of dji they havent responded yet.I hope im missing smth here like a misscalibration or smth couse i dont want to wait forever for a new drone.Oh i forgot the first time i turned it on i used gps hack to get max transmission power but i dont think it has anything to do with that.
 

sar104

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I posted a flight record i watched it on phantomhelp and yes it confirms the changes in the gps lock all the time
Right - but it confirms more than that. Look at the relationship between height and GPS:

gps_height.png

To me that immediately suggests that there is a ground source of GPS jamming or interference somewhere in that region, and as the aircraft climbs the interference gets stronger.
 

Geri87

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Right - but it confirms more than that. Look at the relationship between height and GPS:

View attachment 98374

To me that immediately suggests that there is a ground source of GPS jamming or interference somewhere in that region, and as the aircraft climbs the interference gets stronger.
Ok first thank you for your time.What do you mean by ground source of gps jamming?I noticed all the time that as i try to go high it lowers the gps signal.Tomorrow i ll try a spot out of the city and lets see.
 

sar104

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Ok first thank you for your time.What do you mean by ground source of gps jamming?I noticed all the time that as i try to go high it lowers the gps signal.Tomorrow i ll try a spot out of the city and lets see.
A few countries employ permanent ground-based GPS jamming systems in the vicinity of sensitive facilities. Others, such as the US, do intermittent GPS interference tests at various locations, which are announced via NOTAM. In your case I'd suspect the former.
 
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Geri87

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A few countries employ permanent ground-based GPS jamming systems in the vicinity of sensitive facilities. Others, such as the US, do intermittent GPS interference tests at various locations, which are announced via NOTAM. In your case I'd suspect the former.
I highly doubt it.I live in a small country,high tech is difficoult to find here,besides i have had already another mavic mini and had no issues at all regarding gps.I can post a log file of my old mavic mini from 2 months ago.
 

sar104

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I highly doubt it.I live in a small country,high tech is difficoult to find here,besides i have had already another mavic mini and had no issues at all regarding gps.I can post a log file of my old mavic mini from 2 months ago.
Well either way - ground-based interference with the GPS/GLONASS satellite signals is the only reasonable explanation for those data.
 

Geri87

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Well either way - ground-based interference with the GPS/GLONASS satellite signals is the only reasonable explanation for those data.
Ok so i tried today outside the city like 2km away on the top of a hill lot of trees but plenty of open space.Much much better although had 3-4 times loss of sats but came back.Dont know what to think.Here is the fly log.
 

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sar104

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Ok so i tried today outside the city like 2km away on the top of a hill lot of trees but plenty of open space.Much much better although had 3-4 times loss of sats but came back.Dont know what to think.Here is the fly log.
That one is inconclusive, but there is still a lot of variation in the number of satellites locked, which is not normal.
 
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The MavicMini .DAT has a gps_hw_status record that contains a "jamind" signal.
1586610899219.png
gps_hw_status is a DatDefined record so you'll have to include the DatDefined records
1586610994971.png

@Geri87 can you provide FLY029.DAT so we can take a look?
 

Geri87

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BudWalker

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Yes sure fly029 is in the city yesterday.And fly039 are both from rural test today.
I don't see anything significant in the gps_hw_status data. Looking at the GPS record just confirms that there was a loss of satellites. FLY029 suggests that the loss is height related but FLY039 doesn't show that correlation. I'm thinking there is a HW problem with the GPS module.
 

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Looking a little further into this it does seem that the MM thinks it's GPS is being jammed. I had originally looked at the jamind data which doesn't look correlated with loss of sats. In this plot the red trace is jamind and the black trace num of sats.
1586618916545.png

However, there is another signal, jammingState, that does correlate with the loss of sats. In this plot jammingState is shown with the background color
1586619097051.png
You may be wondering what these signals actually mean. I don't have a clue.
 
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Geri87

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Looking a little further into this it does seem that the MM thinks it's GPS is being jammed. I had originally looked at the jamind data which doesn't look correlated with loss of sats. In this plot the red trace is jamind and the black trace num of sats.
View attachment 98421

However, there is another signal, jammingState, that does correlate with the loss of sats. In this plot jammingState is shown with the background color
View attachment 98422
You may be wondering what these signals actually mean. I don't have a clue.
I know for sure that since i live in europe the regulations are more strict than the us but thats with the transmission power of the remote dont know how the drone can be affected looks impossible.I can do more tests but it would be easier to replace the gps module than to get it back for replacement to dji i suppose.
 

Geri87

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If it changes anything this is my MM.It has 2 gears,rcgeek strobflash and a gimbal shield.I dont think they mess with anything.One thing i tried today outside my apartment starting with no gps inside then when it got out of the window (had the propguard attached to see any reaction) it says payload message and had 0 sats cpuld find sats ,and then i landed it in the street restarted the remote control then the drone picked 6 or 5 sats(why it picks sats if i restart the rc and not when was already connected when it gor out from my window???).take off from the street it said max altitude reached 4.5 meters!!!had to go down to reach for it it couldnt go up more than this.Strage maybe too weight.
 

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