OpenStick adventures Part 2: GPS

It would be great if the GPS part of the modem could be used.

Modem manager supports this, and it should be as simple as running the command below:

sudo mmcli -m 0 --location-enable-gps-nmea --location-enable-gps-raw --location-enable-3gpp

This command enables NMEA and Raw output as well as the coarse network location derived from the mobile network.

I have yet to acquire any satellite signals.

sudo mmcli -m 0 --location-get
... 3GPP Output cut ...
  --------------------------
  GPS  |               nmea: $GPGSA,A,1,,,,,,,,,,,,,,,*1E
       |                     $GPRMC,,V,,,,,,,,,,N*53
       |                     $GPVTG,,T,,M,,N,,K,N*2C
       |                     $GPGGA,,,,,,0,,,,,,,,*66

The first line shows that no satellites are available and the rest just confirm that no fix is possible.

The link below shows common NMEA sentences and how to decode them properly.

https://pe2bz.philpem.me.uk/Comm/-%20Receivers/-%20GPS/Info-921-GPS/Site1/Gps-Diags/NMEA_sentences.htm

Maybe I need to find a better location to put the stick and give it longer for a cold fix. The building I am in has thick stone walls and I haven’t found a suitable location for a power supply that has good visibility of the sky. I might try the conservatory over night.

AGPS

Augmented GPS should, in theory massively improve fix times on basic GPS devices. there are two modes of operation MSB and MSA. MSB is a simpler mode where an aGPS server is used to proved network time, this can reduce the time taken to get an initial fix. MSA lets the aGPS server carry out much more of get calculation required. This is provided by fewer aGPS providers.

In my experimentation I was able to enable MSA, but reveived and error when I tried to enable MSB. I am currently not sure whether this is due to a configuration error (URLS and servers) or an issue with my modem.

The flags: --location-enable-agps-msb and --location-enable-agps-msa are used to control this behaviour.

When enabling MSB mode I receive the following error:
error: couldn't setup location gathering: 'GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Aborted: Couldn't enable location 'agps-msb' gathering: Failed to receive operation mode indication'

Update 2025/01/15

After nearly 24 hours to acquire a signal there is still no change.
I have to assume that the antenna or other parts required for GNSS are not present or configured properly in these dongles. This would make sense if an active antenna is required or additional hardware for such a cheap device, it would have been just too good to be true.