The BIG GNSS (GPS) Issue -- The Constructive Thread

[Raffaello_IZ0QWM]

I doubt that is the case because it would not explain how the drone performs super fast on the 0300 firmware which I have personally downgraded my drone to and tested. With each iteration of firmware after that namely 0400, 0500, 0600, the GPS lock times have only gotten worse. If the location of the GPS receiver was the issue from the start this drone would have been suffering long gps wait times since the initial firmware which is 0100 of which it was not.

So you've seen the situation get worse?
Here in Italy it has always gone wrong since the first firmware.

 

[Raffaello_IZ0QWM]

Any possibility that their algorithms are not properly taking advantage of the local time zone and of daylight saving time and due to that they are calculating incorrect data that is leading to a delay in locking in the GPS signal?

I've had some various Android based car stereos and none of them were ever coded correctly to handle time zones and things would always be inconsistent. Just throwing that out.

The problem is that we currently don't know which algorithm they use.


This is a patent from DJI about GNSS:

CN108513623B - Pseudo-range calculation method and terminal - Google Patents

A pseudorange calculation method and terminal, computer program product and computer storage medium comprising: acquiring the current time (201) of the local terminal; obtaining a distance (202) between the terminal and an out-of-lock satellite, the out-of-lock satellite being a satellite that...

patents.google.com

WO2019019044A1 - Pseudorange calculation method and terminal - Google Patents

A pseudorange calculation method and terminal, computer program product and computer storage medium, the method comprising: obtaining the current local time of a terminal (201); obtaining a distance between the terminal and a lost-lock satellite (202), the lost-lock satellite being the satellite...

patents.google.com

 

[ZoneAerial]

While there were not specific reports of long acquisition time on early firmware there were a fair number of reports of poor GPS performance with stability and flight and I actually mentioned this in my review. I think people should start to think that way of what DJI may have addressed in later firmware.

There is no evidence there is more than one module and im going to say now i am strongly of the opinion the hardware is absolutely fine and comparing M3 GPS to MA2 is not apples for apples.

I have a LOT of data already and im starting to come to some conclusions and while im not ready to spell it out yet im hoping to by end of the weekend/early next week.

I am also going to be clear that while I can confirm somethings I will be giving an opinion on the issue and that is as always going to be open to debate but it will be fact based on actual data. One thing for sure is people need to stop talking about sat count as it close to means bugger all once you are over 8. Positional accuracy and HDOP and PDOP are the key data.

Oh, so you are going to solve the problem in your garage that a billion dollar company can’t fix in many months? Amazing!

Remember when they promised that it would acquire GPS “faster than ever” because of their special “algorithm”?

 

[ianwood]

Oh, so you are going to solve the problem in your garage that a billion dollar company can’t fix in many months? Amazing!

Mad never said he was going to solve the problem. He said he was going to investigate it to see if he can uncover more about the cause. Which, I might add, is what this thread is about.

Learning more about the problem helps us put pressure on DJI to solve it. I imagine you might support that, no?

 

[ianwood]

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Most of those parameters look like they are not related to configuring the GPS receiver though it is impossible to know for sure. However, I see a bunch relating to FDI which could very well reference Fault Detection and Isolation.

I am beyond my knowledge set at this point, but a quick search reveals that FDI is a method of filtering SVs in order to use only the healthiest ones as a means of improving DOP. Sound familiar?

(Caveat: There are also parameters referencing RTK which would suggest not all are relevant or used by Mavic 3 and may simply be there for some other product using the same codebase.)

There are papers about different FDI schemes including ones that go beyond simple SNR limits. Here is an excerpt from an abstract:

In conventional approaches, each GPS signal received is analysed to determine if it is contaminated and only the clean signals are used for positioning the current location. This feasibility test is called an FDI scheme, and it is commonly used in commercial GPS receivers, where only the signal-to-noise ratio (SNR) is used to detect false GPS signals. On the other hand, in urban environments or near buildings, the selection of satellite signals by the SNR only is unreliable, which results in an insufficient number of satellite signals to position a transporter at a certain moment.

I need to look at the patents @Raffaello_IZ0QWM linked to as they seem related. The "simulator" GPS parameters specifically are interesting.

 

[Meta4]

Learning more about the problem helps us put pressure on DJI to solve it. I imagine you might support that, no?

It's a basic part of the drone that's not functioning properly.
You shouldn't need to identify the fine details of the cause of the issue to be able to put pressure on DJI.

 

[ianwood]

It's a basic part of the drone that's not functioning properly.
You shouldn't need to identify the fine details of the cause of the issue to be able to put pressure on DJI.

While I agree that the issue is fundamental enough as it is that DJI cannot ignore it, learning more about the issue informs and empowers users.

 

[Suren]

Most of those parameters look like they are not related to configuring the GPS receiver though it is impossible to know for sure. However, I see a bunch relating to FDI which could very well reference Fault Detection and Isolation.

I am beyond my knowledge set at this point, but a quick search reveals that FDI is a method of filtering SVs in order to use only the healthiest ones as a means of improving DOP. Sound familiar?

(Caveat: There are also parameters referencing RTK which would suggest not all are relevant or used by Mavic 3 and may simply be there for some other product using the same codebase.)

There are papers about different FDI schemes including ones that go beyond simple SNR limits. Here is an excerpt from an abstract:


I need to look at the patents @Raffaello_IZ0QWM linked to as they seem related. The "simulator" GPS parameters specifically are interesting.

This level is beyond me

 

[Mad_Angler1]

Serials Baud rates, GSP Cycles rate and low power mode changes result in negligible differences in Time To Lock, 3D Fix or overall HDOP and horizontal accuracy. It could add 10-15 seconds possibly at worst in my tests not nothing substantial or anything outside of error.

It’s not this or these issues based on my tests.

 

[Suren]

Serials Baud rates, GSP Cycles rate and low power mode changes result in negligible differences in Time To Lock, 3D Fix or overall HDOP and horizontal accuracy. It could add 10-15 seconds possibly at worst in my tests not nothing substantial or anything outside of error.

It’s not this or these issues based on my tests.

Im just grasping at straws but read my recent thread which is just based on my own theory and speculation and tell me im crazy.

 

[ianwood]

Serials Baud rates, GSP Cycles rate and low power mode changes result in negligible differences in Time To Lock, 3D Fix or overall HDOP and horizontal accuracy. It could add 10-15 seconds possibly at worst in my tests not nothing substantial or anything outside of error.

It’s not this or these issues based on my tests.

Yes but what about a proprietary method of filtering SVs to improve HDOP?

 

[Manu64]

New information from my request to DJI (I'm french, so I have used a translator to convert to english) Support3.NL (DJI Support) 6 Apr 2022, 19:34 UTC+8 Hello Emmanuel, Thank you for contacting DJI EU support. We have just received an internal note regarding your GNSS/GPS reception time issue on the Mavic 3. Following the last update, we are finding that some users are still experiencing reception/timeout issues, especially in high latitude areas. You can therefore ignore our previous email requesting flight history information from the drone and the application. We have also detected that the presence or absence of an internet connection on the mobile device/remote control can also affect the reception time. If this is connected to the internet, the reception will be faster. The source of the problem has been located and a new update is planned, which will be issued in the next two months. We apologize again for the problem encountered and we are doing everything necessary to restore the proper functioning as soon as possible. Do not hesitate to contact us for any question. Thank you for your confidence. Thank you for choosing DJI. Marc Support3.NL DJI NL Technical Support

 

[Dougcjohn]

@Manu64 Well, that's a positive response!
More response that DJI typically provides.
1) reconized the on-going issue, 2) provides an est when next update to correct can be expected.

Nice to provide to the group.
Hopefully they'll follow through!

 

[zinko]

But...wait another two months for gps fix?

 

[Jagerbomb52]

DJI acknowledges continued Mavic 3 GPS issues, states fix to come 'within the next two months'

Mavic 3’s GPS connection problem has been known for quite some time now, and the most recent firmware update was...

dronedj.com

 

[Dougcjohn]

But...wait another two months for gps fix?

Lol... that will include multiple new features and enhancements... plenty more things to need later correction.
Kidding of course

 

[VenomXts]

Lol... that will include multiple new features and enhancements... plenty more things to need later correction.
Kidding of course

The GPS issue will be fixed but the drone will no longer fly. What a train wreck for a flagship drone.... jebus.

 

[Dougcjohn]

The GPS issue will be fixed but the drone will no longer fly. What a train wreck for a flagship drone.... jebus.

2 month's... the release of the M3S...

 

[Suren]

New information from my request to DJI (I'm french, so I have used a translator to convert to english) Support3.NL (DJI Support) 6 Apr 2022, 19:34 UTC+8 Hello Emmanuel, Thank you for contacting DJI EU support. We have just received an internal note regarding your GNSS/GPS reception time issue on the Mavic 3. Following the last update, we are finding that some users are still experiencing reception/timeout issues, especially in high latitude areas. You can therefore ignore our previous email requesting flight history information from the drone and the application. We have also detected that the presence or absence of an internet connection on the mobile device/remote control can also affect the reception time. If this is connected to the internet, the reception will be faster. The source of the problem has been located and a new update is planned, which will be issued in the next two months. We apologize again for the problem encountered and we are doing everything necessary to restore the proper functioning as soon as possible. Do not hesitate to contact us for any question. Thank you for your confidence. Thank you for choosing DJI. Marc Support3.NL DJI NL Technical Support

So, like I said a new FW coming t improve the sats problem only, but no more downgrading will be available.

 

[Meta4]

DJI acknowledges continued Mavic 3 GPS issues, states fix to come 'within the next two months'

Mavic 3’s GPS connection problem has been known for quite some time now, and the most recent firmware update was...

dronedj.com

So they've had 4 months trying to fix this and now say they've identified the problem.
They said that their previous firmware update would fix it.
But it will take another two months to fix it now.
At this point, you have to wonder if they are able to do anything about the problem.
If a mechanic gave me this runaround, I'd take the car to a different mechanic.