Bangle2.js GPS performance

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  • Is anyone else finding that the GPS performance of the Bangle2.js is significantly worse than that of the Bangle.js? I ran this code on the Bangle2 and placed it outside on a south-facing window ledge:

    var max=0;
    var count=1;
    var max_count=1;
    Bangle.setGPSPower(1);
    Bangle.on('GPS',function(fix){console.lo­g(fix.satellites + ' satellites at ' + count + 's, max is ' + max + ' at ' + max_count +'s');if (fix.satellites>max){max=fix.satellites;­max_count=count;}count=count+1;});
    

    After 20 minutes it was seeing 7 satellites, a total which had been reached around 6:30 in and remained consistent from then on. I uploaded GPS data (GPS only) and ran it again; this time it had seen 11 satellites within 2 minutes although the total varied between 7 and 10 until the 20 minutes was up.

    I thought uploading the data was only supposed to decrease time to fix, but it looks like it somehow determines whether the sketchier satellites will be visible at all. For the original Bangle.js you also have a choice of how many days' worth of GPS data to upload, but for the Bangle2.js there is no indication of how long it will be valid for. All that aside, when wearing both watches at the same time and saving a GPS track, the Bangle.js invariably does a far more accurate job.

  • There are different GPS chips in Bangle Js 1&2 and as a result they perform differently. The JS1 ublox chip gets a fix within 1-2 minutes even without AGPS data. The Bangle 2 chip takes longer to get a first fix and the AGPS data expires within 6 hours instead of 24 hours for the ublox chip. I think the expiry time is set by the chip manufacturer that supplies it. The chip in the JS2 comes from a Chinese manufacturer and is not well documented.

    In my experience of using GPS devices, after about 4 satellites you have a GPS position and adding in more satellites does not make noticeable well.

  • and the AGPS data expires within 6 hours

    Are you sure about this? I was pretty sure the data was 48 hours (but it's not updated that often so realistically any upload would be valid for 24)

    I thought uploading the data was only supposed to decrease time to fix, but it looks like it somehow determines whether the sketchier satellites will be visible at all

    On Bangle.js 2 the upload also configures what the GPS is searching for (with the radio buttons). That's something that could be done with an app too, but it just made sense to stick it in the AGPS upload.

    If you're not also searching for Galileo and Beidu then it can use more resources to search for GPS, which is why it can see more.

    ... but yes, sadly the Bangle.js 2 GPS isn't quite as good as the Bangle.js 1. Part of that is the chipset, but part of that is also that the device itself is a lot smaller and so there's not as much room for a good aerial.

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Bangle2.js GPS performance

Posted by Avatar for skm @skm

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