GPS recording at interval +1s

Hi Gordon,
I've designed and programmed my personal GPS devices based on M8N and M9N.
Data from a Ublox chip normally is very accurate, but I use the binary protocol and not NMEA.

Attached are 2 files, 1 is data from the Bangle, the other is from my own logger at 5hz.
I've highlighted the suspicious part in the Bangle screenshot.

When I look at the track points

  <trkpt lat="52.477275" lon="5.065324">
    <ele>-5.9</ele>
    <time>2021-06-22T14:50:57.000Z</time>
  </trkpt>

  <trkpt lat="52.477113" lon="5.065425">
    <ele>-12.3</ele>
    <time>2021-06-22T14:50:58.000Z</time>
  </trkpt>

There is 19m between them, 19m/s = 68,4km/h

For my personal devices I use double for lat/lon data, it almost looks like the current grid is not dense enough.

I used km/h NMEA data from the Ublox on another Bangle and it is spot on! (other wrist)
So I really suspect the lat/lon data from the recorded file.

The Ublox spec has 8 digits, the recorded file 6 (page 141)
https://www.u-blox.com/en/docs/UBX-13003221

Could it be the difference between 32 and 64 bit?

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