I have a NEO-M9N (GPS-15712) connected to an Openlog Artemis via QWIIC, and am logging position and time. The question concerns mainly the lack of precise agreement between the two "gps times", TOW and UTC.
1) I'm trying to log 5 times a second but am only getting data logged every 400 ms. I assume that's because with this sensor I'm pushing the Artemis too hard. Is this correct?
2) The fractional part of the seconds in UTC is reported always as an integer times 200 ms (e.g. .000 or .400, and never .023 or .417). This seems contrived. Is it how the NEO-M9 reports UTC, or is it a function of the OLA firmware?
3) The time reported in TOW is different from UTC by 200 ms. Actually this is the difference in the fractional part of the seconds. (I'd expect these to be different by an exact integer number of seconds, zero or 18). This discrepancy seems odd, so does it have a simple explanation? (If I change the logging rate to 2 per second, this difference becomes 500 ms).
Here are some sample lines of logged data with the headers. The TOW is apparently in milliseconds and is the 2nd last number in each line. The first date and time in each line is that of the OLA. The second date and time is UTC reported by the NEO-M9.
31/10/2020 01:18:51.64,31/10/2020 01:18:51.800,-348546954,1387039616,124498,13,3,0,157,0,211,523150000,2.98
31/10/2020 01:18:51.99,31/10/2020 01:18:52.200,-348546850,1387039613,127225,17,3,0,36,0,184,523150400,2.75
In the second line the fractional part of the UTC time is .200 s and in the TOW it is .400 s .
Thanks for any help in sorting this out,