4 ms·
GPS modules need to be put in a special stationary mode (and ideally measured-in to a location for a day or two) to get accurate timing. I'm consistently achiev
by eqvinox 1y ago
GPS modules need to be put in a special stationary mode (and ideally measured-in to a location for a day or two) to get accurate timing. I'm consistently achieving ca. 10ns of deviation. Hope the author didn't forget this. (But it might also just be crappy GPS modules, I'm using u-blox M8T which are specifically intended for timing.)
- RossBencina 1y agoWhat method do you use to measure 10ns deviation?
- eqvinox 1y agoDelta between modules on a scope (offset values on the hardware timestamp on the immediately connected PTP clock also line up with this) [Caveat: everything is in the same room with the same ambient temperature drifts…]
- mwpmaybe 1y agoInteresting. The serial GPS module currently wired up to my Raspberry Pi doesn't have a stationary mode per se but there is a feature called AlwaysLocate that seems related. I can choose between Periodic Backup/Standby and AlwaysLocate Backup/Standby modes. I'll need to look into this... ETA: I can also increase the nav speed threshold to 2m/s.
- eqvinox 1y agoNot all modules have this feature; and it's also locked behind feature/license bits sometimes. It's obviously not needed for normal GPS use… u-blox timing targeted modules definitely have it. Some have a "measure-in" mode where you let it sit for a while (days) and it does all the setup automatically. Other cases you actually have to feed things into the module (annoying and error prone…) It's simply that if you know your location, you can remove that as free variable from the equations and instead constrain the time further.