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  • Data Question

    Looking at the data table on the Dump1090-fa screen I see the data in the attached image

    According to the key at the bottom most data is ADS-B which I expect as I have an ADS-B receiver, however the blue highlighted data is shown as Other.

    Where is this data coming from, and why is the speed and heading data missing?

  • #2
    Mode-S
    The under-laying technology within ADSB (adsb isn't a thing, but more a term covering many broadcast technologies used)

    The diffeence, is no GPS input for position data.

    https://en.wikipedia.org/wiki/Second...e_radar#Mode_S

    The dead giveaway is the heading at the top total vs 'with positions'
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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    • #3
      OK Thanks!
      So the Mode-S data is still transmitted using the same transmitter/frequency/coding as the ADS-B data... just not connected to a GPS?

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      • #4
        Yes. More or less:

        Mode-C = signal from spinning SSR at airport, triggers reply from aircraft (we dont see)
        Mode-S = Broadcasts out without interrogation FROM aircraft - HEX code assigned, transmits Alt/Speed
        ADSB = Mode-S+GPS (mode-s Extended Squitter (more data))

        http://web.mit.edu/6.933/www/Fall2000/mode-s/today.html
        Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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        • #5
          Mode-S and Mode-C transponders are both interrogated by radars.
          Mode-S transponders will also send out extra DF11 messages without interrogation (squitter).

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          • #6
            OK thanks very much for the replies....sorry but I now have one more question...

            So the aircraft with Modes-S that I am receiving, do not plot on my Dump1090-FA map, obviously because they dont have a GPS position.... But yet I can see those aircraft positions being plotted on the Flightradar24 map... how does FR24 know the position?


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            • #7
              Originally posted by kiwiandy View Post
              OK thanks very much for the replies....sorry but I now have one more question...

              So the aircraft with Modes-S that I am receiving, do not plot on my Dump1090-FA map, obviously because they dont have a GPS position.... But yet I can see those aircraft positions being plotted on the Flightradar24 map... how does FR24 know the position?

              The other column listed in yours. MLAT

              https://www.flightradar24.com/how-it-works
              Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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              • #8
                Perfect.. thanks very much

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                • #9
                  Sorry, but one more question.....)
                  How does DUMP1090-fa know what the size aircraft is and what image size to use?
                  2019-12-11 13_53_18-PiAware Skyview - 7_10 - Brave.png2019-12-11 13_53_18-PiAware Skyview - 7_10 - Brave.png

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                  • #10
                    The same way fr24 does (in how it works)

                    None of that info is from planes. (Incl registration)

                    It looks up online databases. Where you can hold a database with the details and match it with hex code.
                    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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                    • #11
                      Yeah that makes sense! thanks again

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                      • #12
                        Sorry, but one more question on this subject!
                        My next door neighbor has a helicopter, which has Mode-s transponder, and switched on, yet he doesn't appear in my list, or on the FR24 maps?

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                        • #13
                          Mode-s. Or Mode-C. It may be a secondary/ATC requested vs broadcast
                          What reg?
                          Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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                          • #14
                            Originally posted by Oblivian View Post
                            Mode-s. Or Mode-C. It may be a secondary/ATC requested vs broadcast
                            What reg?
                            Sent you via PM

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                            • #15
                              Look for options to show positionless aircraft. May have it turned off.

                              It does show I have logs as early as yesterday. But it doesn't appear to have GPS integration LAT/LON - So only MLAT

                              As MLAT works best above 2000ft... it will be patchy at best. You won't see MLAT positions on local map as FR24 doesn't feed it back.

                              And on their map, it needs to be well covered
                              Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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