@Loly
Your English may not be perfect but your brain works very well. As far as i'm concerned you've solved the accuracy problem. My de-bricked 3590 is now showing rock-sold 3m like 37xx and 35/34xx out of the box. I think this procedure should be a final step after any fw cure is done too.

My 3490 convert improvement is not quite so dramatic as the 3590, but it's now showing 3 m while locked on to only 7 to 8 GPS sats + 1 SBAS sat (PRN 193 this time). When accuracy was 4 m or worse there was no SBAS lock and even with up to 10 GPS sats it could only manage 6m at times without SBAS. In this test, it seemed every time it lost the SBAS fix, it lost accuracy. But mostly it showed 3-4 m particularly when stopped, and never worse than 6m and that was only when moving and so briefly that I had trouble getting the screenshot of 6m. As soon as I'd stop to do the screenshot, accuracy would improve within seconds by a metre or two. i.e. 6m went quickly to 5 or 4 m etc. Conditions much the same as the other two tests (mostly cloudy). Vertical accuracy now seems more believable in 3490 too, and it's fix time is dramatically improved. Moving accuracy while not as good as stationary is most acceptable to me.

None of this explains why some users like giuseppe66 previously were getting 15-20 m while others like me, Caty & voyager56 were never getting worse than 10 m though. If all the other unfortunates can now get 5-6m with this procedure like reported above by giuseppe66 they should be happy imo. Screenshots are of 3490, I didn't bother with the 3590 as it was 3 m all the time, stopped or moving.

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I believe we have found our Hero on this. Loly, please have your Missus give you a big wet kiss from me.