Speed up 1PPS / provide a fix with fewer satellites

RE: Speed up 1PPS / provide a fix with fewer satellites

Hakon — Tue, 10 Dec 2024 10:00:58 GMT

Thank you.

RE: Speed up 1PPS / provide a fix with fewer satellites

tommy99 — Fri, 15 Nov 2024 10:00:41 GMT

Feature -- Add a "fixed position" mode where the position of the device is known so that one satellite lock provides the 1PPS pulse (lower accuracy would be acceptable) for synchronization purposes

RE: Speed up 1PPS / provide a fix with fewer satellites

Hakon — Thu, 14 Nov 2024 09:39:34 GMT

If you can write here concretely what you want as a feature, I can submit a feature request internally.

RE: Speed up 1PPS / provide a fix with fewer satellites

tommy99 — Tue, 05 Nov 2024 11:02:19 GMT

Hi Hakon, thanks for the response!

1. We already set the position and altitude using nrf_modem_gnss_agnss_write (where we set the position along with the altitude). That seems to work since 3 satellites are enough to get the position fix (in the combination with the low accuracy mode).

location.latitude          = latitude_m; /* Best estimate within maximum limit of 1800 km. */
location.longitude         = longitude_m;/* Best estimate within maximum limit of 1800 km. */
location.altitude          = altitude;   /* Actual altitude of the device in meters. */
location.unc_semimajor     = 0;          /* Uncertainty, semi-major. Range 0...127 or 255. */
location.unc_semiminor     = 255;        /* Uncertainty, semi-minor. Range 0...127 or 255. */
location.orientation_major = 0;          /* Set to 0 if unc_semimajor and unc_semiminor are identical values. */
location.unc_altitude      = 0;          /* Uncertainty, altitude. Range 0...127 or 255. */
location.confidence        = 100;        /* Set to 100 for maximum confidence. */

if(nrf_modem_gnss_agnss_write(&location, sizeof(location), NRF_MODEM_GNSS_AGNSS_LOCATION) != 0){
    LOG_ERR("Failed to set nrf_modem_gnss_agnss_write");
}

2. Is there a feature request interface where this could be added and voted on (perhaps others would benefit from the feature as well)?

RE: Speed up 1PPS / provide a fix with fewer satellites

Hakon — Tue, 05 Nov 2024 09:47:17 GMT

Hello,

[quote user=""]1. Do you have any other suggestions for the configuration that we could use to speed up getting the valid 1PPS pulse and make it more robust in the weaker signal strength situations (indoor near a window / on the balcony)?[/quote]

You can try setting CONFIG_GNSS_SAMPLE_ASSISTANCE_REFERENCE_ALT to reference altitude. You should also take a look at the response in this ticket https://devzone.nordicsemi.com/f/nordic-q-a/96546/gps-takes-long-time-to-fix-satellites-pop-in-and-out-of-tracking?ReplyFilter=Answers&ReplySortBy=Answers&ReplySortOrder=Descending

[quote user=""]2. Would it be feasible to add a "fully fixed position" mode support where the position of the device is known so that fewer satellite locks could provide the 1PPS pulse (lower accuracy would be acceptable)?[/quote]

It could be feasible, but I'm not sure that will be prioritized by the modem team right now. It is something to consider in the future though.