Follow me says Weak Satellite app says 16

[shadesofblack]

Hey folks,

Second post and question if anyone experienced this happening?

Equipment, iPhone 7 Plus, DJI GO 4 App and latest firmware on controller, Mavic and course batteries.
Area, large open (Australian) footy pitch no interference.

Orbit and active track fine but when trying follow me up comes with weak satellite and yet app says 16.

Dr Google not helping, so wonder if anyone here found the same?

Also I fly in Aircraft mode as I don't want a call or iMessage etc while flying.

Thanks.

 

[davebelton]

Hey folks,

Second post and question if anyone experienced this happening?

Equipment, iPhone 7 Plus, DJI GO 4 App and latest firmware on controller, Mavic and course batteries.
Area, large open (Australian) footy pitch no interference.

Orbit and active track fine but when trying follow me up comes with weak satellite and yet app says 16.

Dr Google not helping, so wonder if anyone here found the same?

Also I fly in Aircraft mode as I don't want a call or iMessage etc while flying.

Thanks.

Had same issues yesterday will be following this

 

[shadesofblack]

@davebelton, glad to see I'm not alone in this one. Hopefully someone has insight to this.

 

[bakerboy]

It's not the mavic with poor gps, it's your phone

Take it off airplane mode and report back to us

No issues with flying with it on, perhaps turn on do not disturb if you're worried about calls

 

[shadesofblack]

@bakerboy, thanks for reply.
Three flights this afternoon one in airplane mode other two with 3 bars 4G
Yes of course DND mode on iPhone
Various apps on iPhone show same number of satellites very strange.

 

[shadesofblack]

@bakerboy, thinking about your reply I'll try tomorrow to move to another flying field with stronger 4G connection and let you know, thanks again for reply.

 

[Anthony]

Ok guys ... page 57 of the user guide covers the operation of this function

"A virtual tether is created between the aircraft and the mobile device so that the
aircraft can track your movement as you move. Note that Follow Me performance is
subject to the GPS accuracy on the mobile device."

This has nothing to do with the number of satellites the mavic can see this is the gps conection your mobile phone or tablet has.

 

[bakerboy]

3G/4G connection has no impact either. it's purely your phones inbuilt GPS receiver that isn't working well

 

[shadesofblack]

@Anthony @bakerboy, thanks for the clarification will now try other locations and give you my feed back.
@davebelton let me know how you go with this valuable information.

Many thanks.

 

[erikgraham]

3G/4G connection has no impact either. it's purely your phones inbuilt GPS receiver that isn't working well

Location services in iOS uses a combination of built in gps, cellular triangulation, and even wifi. In the US it generally works very well because cell towers are numerous, and Google (and others) have gone around snooping out locations for wifi networks (yes that's an invasion of privacy). Cell tower triangulation does the heavy lifting. Pure GPS on the phone is not very accurate unless you leave the phone out with a clear view of the sky and don't move it for a few minutes.

However, in rural areas where cell towers are sparse, location accuracy is reduced.

 

[Scottmagner]

have never been able to get mine to work and neither has any of my friends. Ive had 2 mavics same issue. 4 other friends mavic. It is most certainly a dji thing they will turn on in an update. Follow me with the phone tracking. Always says poor satellites.

 

[shadesofblack]

Will check it out tonight with GPSdiagnostic app on iPhone and post findings.

 

[andynormancx]

In the US it generally works very well because cell towers are numerous, and Google (and others) have gone around snooping out locations for wifi networks (yes that's an invasion of privacy). Cell tower triangulation does the heavy lifting. Pure GPS on the phone is not very accurate unless you leave the phone out with a clear view of the sky and don't move it for a few minutes.

This isn't true. Cell tower triangulation and wifi only give very rough location data.

When an app asks iOS for location data it specifies how accurate it wants the data to be. If the app asks for low accuracy data then iOS will just rely on cell tower and wifi information to give a rough location. In these cases iOS avoids turning on the GPS receiver as much as possible (to preserve battery life)

That isn't what the DJI app does that, it requests the most accurate location data that iOS has available, which means iOS turns on the GPS receiver. An iPhone will typically get a highly accurate (for consumer GPS) location in a few seconds. It doesn't normally take minutes to get a solid location lock on an iPhone when you are out in the open.

This is because unlike your typical dedicated GPS receiver the iPhone will fire up the GPS receiver on a regular basis, even when an app isn't asking for high resolution location data, to get keep the data it needs for a quick lock up to date. My iPhone always gets a lock much quicker than the dedicated GPS receivers I've used because of this.

The same applies to Android devices too, though there are variation on how well it all actually works between devices.

 

[andynormancx]

This isn't true. Cell tower triangulation and wifi only give very rough location data.

When an app asks iOS for location data it specifies how accurate it wants the data to be. If the app asks for low accuracy data then iOS will just rely on cell tower and wifi information to give a rough location. In these cases iOS avoids turning on the GPS receiver as much as possible (to preserve battery life)

That isn't what the DJI app does that, it requests the most accurate location data that iOS has available, which means iOS turns on the GPS receiver. An iPhone will typically get a highly accurate (for consumer GPS) location in a few seconds. It doesn't normally take minutes to get a solid location lock on an iPhone when you are out in the open.

This is because unlike your typical dedicated GPS receiver the iPhone will fire up the GPS receiver on a regular basis, even when an app isn't asking for high resolution location data, to get keep the data it needs for a quick lock up to date. My iPhone always gets a lock much quicker than the dedicated GPS receivers I've used because of this.

The same applies to Android devices too, though there are variation on how well it all actually works between devices.

 

[erikgraham]

This isn't true. Cell tower triangulation and wifi only give very rough location data.

When an app asks iOS for location data it specifies how accurate it wants the data to be. If the app asks for low accuracy data then iOS will just rely on cell tower and wifi information to give a rough location. In these cases iOS avoids turning on the GPS receiver as much as possible (to preserve battery life)

That isn't what the DJI app does that, it requests the most accurate location data that iOS has available, which means iOS turns on the GPS receiver. An iPhone will typically get a highly accurate (for consumer GPS) location in a few seconds. It doesn't normally take minutes to get a solid location lock on an iPhone when you are out in the open.

This is because unlike your typical dedicated GPS receiver the iPhone will fire up the GPS receiver on a regular basis, even when an app isn't asking for high resolution location data, to get keep the data it needs for a quick lock up to date. My iPhone always gets a lock much quicker than the dedicated GPS receivers I've used because of this.

The same applies to Android devices too, though there are variation on how well it all actually works between devices.

This is 1000% wrong. Totally inaccurate.

Do some research. Start here: Assisted GPS - Wikipedia

Google multipath effect as well.

Then move on to Apple's developer support pages, starting here: Getting the User’s Location

And remember, cell phones rarely if ever have an unobstructed view of the sky unless you deliberately take it out of your pocket (or car) and hold it out away from your body.

 

[andynormancx]

I've done plenty of research thanks. I understand in some detail how the location services work on iPhones.

The iPhone will get a quick accurate fix with its GPS receiver when it can't see a single cell tower, as long as it has recently been in good mobile and GPS coverage area and will do so quicker than your average dedicated GPS device.

Assisted GPS can help out with getting a fix quickly, by providing almanac data for the current satellite orbits. But it is still the GPS receiver on the phone that is providing you with your accurate location data, not cell tower triangulation or wifi AP location data. Assisted GPS doesn't tell the phone where it is, it just provides the details on where the satellite are to make it quicker for the phone's GPS receiver to get a solid lock.

To quote from the "Hybrid positioning system" page linked from the A-GPS page:

"These systems are specifically designed to overcome the limitations of GPS, which is very exact in open areas, but works poorly indoors or between tall buildings (the urban canyon effect). By comparison, cell tower signals are not hindered by buildings or bad weather, but usually provide less precise positioning."

 

[Delano]

I have this issue to when using an iPhone 7.
However when using an iPad Pro through the USB port of the controller it works fine (strong gps signal for follow me) from the same position. That's obviously an iPad that takes a SIM card and therefore has GPS.

So it's not a lack of gps strength in my opinion, just some other issue. If I open any map app on the iPhone from the same location it takes me to as accurate a position as I think gps on a phone can (same as the iPad does).

I just used the iPad to test, don't normally fly with it.

Wonder what the issue is. I see many other have the same to on other forums/google.

Using the iPhone through the USB connection at the bottom of the controller doesn't work either, so not the cable that came with the Mavic.
iPhone has no case on it either.

 

[shadesofblack]

Geez guys, did not mean to start a squabble

So last night (with iPhone 7 plus airplane mode or 4G) I got the exact same results for Satellite connection in my rural area.
Mavic had lock on 17
iPhone had this on image below

 

[andynormancx]

You need to take some of what that app is telling you with a pinch of salt I'm afraid. It is claiming to give you information that simply isn't available to apps running on iOS.

Specifically it is claiming to know:

• whether a location is coming from GPS or cell/wifi
• how many satellites have a lock
• the "quality" level of the signal from individual satellites

None of these bits of information are available to an app on iOS via Apple's API (application programming interface). Either:

• the developer has found some way to bypass the API to get the details it is showing
• the app is misleading in what it is showing

Bypassing the API would get the app banned from the AppStore, so sadly I'm sure it is the second option.

The iOS location API is very restrictive in what it tells apps about how the location was obtained. You request a location, specifying how accurate you'd like it to be. The device then uses cell tower/wifi/GPS/etc and starts sending you location data.

The location data contains the location and information on how accurate iOS thinks the data is. It always provides a horizontal accuracy estimate, in some cases it also provides a vertical accuracy estimate.

It does NOT tell you where the location data came from, it does not tell you that it came from the GPS receiver for example. In fact, iOS will not even tell the app whether the device the app is running on has a GPS receiver or not (apps instead have to maintain a database of device model numbers that have a GPS or assume that those that only those that have mobile data also have* a GPS).

In the past apps could use the fact that iOS was providing a valid vertical accuracy estimate to assume that a given bit of location data came from the GPS receiver. However I suspect that isn't the case now that recent iPhones have barometers (though the Apple documentation still currently claims "Determining the vertical accuracy requires a device with GPS capabilities").

When I've used the API I've seen location data that had a level of horizontal accuracy estimate that indicated it almost certainly came from the GPS, but that didn't have a valid vertical accuracy estimate.

So this app must be just using the accuracy estimates to guess whether it is getting the data from the GPS receiver or not. I can only assume that its claimed satellite quality chart is just some randomised data scaled based on those same accuracy estimates, that data is certainly not available to it through the API (and in 9 years of messing about with GPS stuff on the iPhone I've never seen any suggestion that you can get that data even if you bypass the Apple API).

In summary, look at the accuracy figure, to see how accurate a location fix you are getting, ignore the rest.

For those who are interested, the main Apple API reference page for their location framework:

CLLocationManager - Core Location | Apple Developer Documentation

The page for the location data itself:

CLLocation - Core Location | Apple Developer Documentation

* which was a correct assumption until the Apple Watch 2 was released, that has no mobile data but does have a GPS

 

[shadesofblack]

@andynormancx, thanks for that feed back.
App used is GPS diagnostic GPS Diagnostic

Based upon what your saying and given Apple API restrictions I'll take the pinch of salt

Will try other various locations to see if its location based that does in fact cause the follow me not to work.

Appreciate everyones feed back thus far on this interesting subject