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MLAT, GPS and NTP on Raspberry Pi

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  • MLAT, GPS and NTP on Raspberry Pi

    I tried to search for answers before posting, but found none.

    I have just updated my feeding RPi to the latest version after running an older one for two years. This time I used one of my Raspberry Pi's that has a GPS receiver which I use in order to have (at least one) Stratum 1 NTP server at home.

    In the /etc/fr24feed.ini file I found a setting for MLAT regarding whether to attempt MLAT without a GPS or not. I changed it to "no". Will this, as I hope, mean that the FR24 software will automatically detect the GPS unit and use it for an "auto survey" to determine its location?

    OK, checking the logs (/var/log/fr24feed.log) answers one part of my question: [gps][w]Could not connect to the GPS receiver. My GPS device is /dev/gps0 and since this box is also acting as a Stratum 1 NTP server I would prefer not to use or install gpsd. Any hints on how to make the fr24feed software aware of the GPS receiver?

  • #2
    Doesn't anyone have any information about how to make fr24feed use a fully working GPS for MLAT?

    One way to solve it, much less elegant though, would be to write some code to collect all GPS position data for a day or two and compute an average position from this. It seems redundant since fr24feed might as well do it automatically. Given that there is a setting for the use of GPS for MLAT, it ought to be possible to make it work.


    • #3
      @vinnyspb is on vacation so don't expect any fast answers, but as far as I know we are not using the GPS today for several reasons.


      • #4
        Originally posted by Mike View Post
        @vinnyspb is on vacation so don't expect any fast answers, but as far as I know we are not using the GPS today for several reasons.
        OK, thank you! Then I will just survey my position and use a static one.

        Maybe this would be a better solution anyway, since the Stratum 1 NTP servers ought to get better precision if not burdened by other running programs.

        What kind of time accuracy is needed for MLAT?


        • #5
          I Johan

          There are any new about use of GPS module on Raspberry and MLAT ??
          I have installed the GPS module from the guide of Taylor-stsignal-eu

          I now use the gps only for NTP server but i'm not be able to connect the gps to FR24feed MLAT

          tu hai risolto ??
          Best regards -- mirco -- ik4hps -- T-LIPK2 --


          • #6
            Averaging positions would be bad as receiver ranges are not guaranteed to be symmetrical, but your idea to calculate the home position based on the data it collects is one I had myself also, if you use the gps positions transmitted by planes and also using triangulation on the same messages should in theory be able to provide the receiver location. But if you have a built-in gps device the idea becomes quite absurd since your own gps fix would be far more accurate than any mlat could provide.


            • #7
              Time accuracy can be calculated using the speed of light which is about 30 cm per nanosecond, if your clock is a millisecond off then it means 300 km mlat uncertainty.