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  • Case ID: 330419
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GNSS Scheduled Downloads Interval and Enable/Disable

TravdaTrav

Hi,

I see in the GNSS documentation for the nRF52840 that the GNSS modem performs scheduled downloads in Periodic Navigation mode, and from some testing, I found the download time to be around 1.1 minutes with a default (not sure if it is default) download period of 13.5 minutes. Right now, I only know how to turn it on and off via the nrf_modem_gnss_use_case_set() function, so is a way to configure the scheduled download period to be some user-defined value instead?

What sort of accuracy impact can I expect by completely disabling scheduled downloads, since I'm not sure where/if that information is stored somewhere.

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  • +1

    Hi Travis,

    I think you mean nRF9160.

    NCS document explains about Scheduled downloads:

    A mechanism to maintain GNSS navigation data availability in periodic navigation mode.

    If GNSS only runs long enough to calculate the first usable fix, it is probably never able to download for example almanacs or ionospheric correction data from the satellite broadcast. To ensure GNSS data availability and to improve accuracy in periodic navigation mode, GNSS performs scheduled downloads. When GNSS determines it needs to download ephemerides or almanacs from the broadcast, the fix interval and fix retry parameters are temporarily ignored and GNSS runs continuously for a longer period of time. GNSS performs scheduled downloads until it has downloaded the data it needs. After the downloads, normal operation is resumed. When A-GNSS is used, scheduled downloads are not necessary and you can disable them using the GNSS API. Scheduled downloads are only performed in periodic navigation mode.

    So there is no way to configure the scheduled download period to be some user-defined value instead, since the GNSS satellites and device environment are not fixed. 

    If you disable scheduled downloads, you may get wore accurate in short time and not able to get a GNSS fix at all after a period of time, due to ephemerides and almanacs are out of date.

    Best regards,

    Charlie

  • 0 in reply to Charlie

    Cool, sounds good. I appreciate the fast response.

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