Dual GNSS support for tracking

palinka shared this idea 8 months ago
Collecting votes

New phones like Xiaomi Mi8 have dual frequency GNSS build in. With Android 9 thos phones are capapble of accuracies < 1 meter but therefore the implementation must be changed.

In the app it could be a new option for tracking

Comments (12)

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New mobile devices like Xiaomi Mi8 have new dual GNSS chip Broadcom BCM47755 build in which supports usage of dual frequencies. Since Android 9 Google really supports that as well. As far as I understood continuos GPS detections must be activated in Android developer options. And now the app "only" need to support usage of dual frequencies for tracking as an extra option. Then finally we could record GPS tracks with an accuracy < 1 meter. For reference please check

https://www.youtube.com/watch?v=vywGgSrGODU&feature=youtu.be


https://medium.com/@sjbarbeau/dual-frequency-gnss-on-android-devices-152b8826e1c

https://www.navigation-professionell.de/xiaomi-mi-8-test-gps-galileo-genauigkeit/

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Good day palinka,

if I understand correctly, there is nothing that needs to be changed on the application side.

Support for dual channels is built-in in the device based on 1. hardware support and 2. software support (Android 9+).

So I believe, when you purchase a device with correct hardware support, all GPS based apps will have expected GPS precision.

I'm looking for confirmation from anyone with such device ;). I'm marking the topic as "Completed" anyway if my thinking is incorrect, feel free to correct me, thanks.

Menion

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Hi Menion,

no, the implementation of any app needs changes. Locus as well. And continus GPS detection must be activated in developer options. Very good explanation in the Google video (the first link).

palinka

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My older, low-spec phone has dual GNSS. Well, Locus shows 21 or 22 satellites on a good clear-sky day, so clearly there's a second system besides just GPS. Must be the Russians.

That doesn't seem to mean a real-world accuracy of 1m, but it's certainly enough to help me find geocaches.

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Dual GNSS does not mean more than one supported sattelite system. It means supporting dual frequencies instead of only one for a certain sattelite system like GPS or BeiDou or GLONASS.

I am sure your phone supports more than only GPS.

The purpose of < 1 m accurancy would be helpful for improving OSM.

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Hello palinka,

finally watched mentioned YouTube video & read a few posts and unfortunately, I'm still little confused.

Android 8+ now offer access to RAW measurements, which are raw values (pseudoranges) received from satellites. But what to do with them? They are useful for analyzing and manual compute of locations or for RTK methods used with conjunction of another service like EGNOS or similar that offer additional data. But, for this is needed quite big RTKLib library and also some automatic system for downloading additional data files.

Anyway, this has nothing to do with support for another frequency (L5) am I right? I still think that using of dual channels (L1+L5 for GPS, ...) needs to be supported by hardware GPS chip and is already supported by Android 8+ which automatically compute device location from both available channels. Why it should be different? L5 behave like another satellite so it is just another "satellite" used in the computation of device location, no big magic behind it.

Maybe I'm wrong and I also do not have a device with Dual channel support to confirm it. If so, I'll need to point to any post that gives me a better explanation. Thanks.

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I suppose using the dual frequency satellite signal can be used for extrapolation of data toward the actual value.

It could be able to compensate the frequency dependent signal propagation delay.


Something like the dual numerical solution of differential equation, the 2nd one using a half step, can be used for the extrapolation toward zero step.

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Hi Menion,


the support of the device for dual frequencies needs a special chip like for example the Mi8 has. Apps like GPSTest show the dual frequencies are available in Android. But by itself the standard API in Android does not use this dual frequencies for improving the accurancy < 1 meter. By default the accuracy is not different to normal devices. A special signal processing logic for combining the both frequencies is required for beeing able to reach the accuracies < 1 meter is required. Google did not implemented that into Android 9. But at least they have provided the foundations. So now it is on the apps to implement the logic here (which might be some hard work of course). At least this is how I understood the Google video.

I am dreaming of having GPS tracks with accuracies below 1 meter that I can use for improving OSM.

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Hello,

you think that compute of device location on these dual channel devices currently still use only L1 channel values and L5 values are only available over these new methods (for developers that want to work with them)? Hmm, that's quite unfortunate ... and I think that quite illogical. Google team interest is definitely bringing the precise location to users and these currently available options require that every GPS application, every developer, have to implement own login to compute location from both channels ... weird.

I'll be carefully watching this problematic, but I really believe that with Android 10 will have to come implementation of this directly in Android, otherwise, it does not make too much sense.

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FWIW, Android Q Beta introduction in Android Developers blog does not mention GNSS at all:


https://android-developers.googleblog.com/2019/03/introducing-android-q-beta.html

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I have a phone with dual GNSS chip, and I also really want to see the position with accuracy better than 1 meter in Locus. Are there any news about this functionality?

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I asked Sean Barbeau about this in his new blog post (https://medium.com/@sjbarbeau/tl-dr-dual-frequency-gnss-on-android-table-of-devices-9be4bbb83a7b) and he said:


Apps shouldn’t need to be updated to get more accurate locations from the Location API — in theory the underlying GNSS implementation should take care of this. However, personally I have yet to see good evidence of decimeter-level accuracy from dual-frequency Android devices.

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I have exactly same expectation as Sean (as I wrote before).

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Hello,

But, it seems that the double frequencies give a great stability in the signal, if one makes a recording of trace in fixed mode, one obtains a maximum deviation of 4 m (compared to the point of reference) after one hour, it is little compared to simple frequencies. But they do not seem to increase the accuracy of a trace recorded in the field.

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Hello,

I have a Xiaomi MI9 Locus does not need anything else to display all the satellites, in the page satellites, there are the double frequencies displayed.

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J'ai oublié de dire que nous pouvons voir les doubles fréquences sur la page satellite Locus. En fait, il indique les numéros de satellites en double lorsqu'il y a deux fréquences. 331-331, 303-303.....Ecran de GPSTest.