09-02-2022, 01:42 PM
(08-29-2022, 12:56 AM)biketool Wrote:(08-28-2022, 03:36 PM)vortex Wrote: By the way, I just had to reinstall Mobian and was able to test the GNSS essentially out of the box (I did nothing whatsoever to configure it) with PureMaps and OSM Scout Server (these were the only two things that were configured). I was able to get a decent fix very quickly even though I was riding in a bus with a metal roof.
Does adding gpsd into the mix help make it work better?
Interesting, I had thought the ttyUSB1 port on the modem had to be designated.
As far as I know it lets you use mobile phone networou do initial setup.k signals to get a general location and precise time to bootstrap a satellite fix by scanning for the right satellites.
Did you configure the mozilla location backend, I think that does some of that when you choose yes on that option during the first boot.
I did not configure the mozilla location backend.
Puremaps is using Geoclue behind the scenes and I think Geoclue use ModemManager to get the position (and it knows which ports to use).
Having dug around a bit, you are on the dot that it starts with a time sync from the mobile network and the cell tower to get an initial guess of position. Additionally, the distros now also download AGPS data from the internet and upload it to the modem to get a fix. It is this last step that wasn't present at first. Early on, AGPS upload was not in virtually any of the distros and did not work well. I think it was SUSE that was the first non-android based one to get it working in the distro itself (quite a few people had done proof of concepts). I think later it got added to eg25-manager, but I am not sure. Anyhow, after that it spread around. Without AGPS, it can take a very long time to get a fix with the tiny antennas and poor positioning that is on modern cell phones. The satellites transmit their orbital information, but with poor reception like cell phones have, it is often garbled and they have to wait again. This is why, before AGPS, fixes took so long and the cell phone had to be outside with the antenna facing up. With AGPS, that bit is solved and they can get a fix quite quickly despite terrible reception.