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Low helicopters in a valley

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  • Low helicopters in a valley


    I have been feeding ADS-B information up to FR24 for a few weeks now,
    but I frequently see aircraft with my eyes and not on the FR24 web site,
    especially when flying at lower altitudes.

    I live in a valley so it’s possible that I am the only receiver who is able to pick up the low
    flying medical helicopters that come in and out of the trauma center, located about half a mile from me.

    One particular flight happened this morning…
    [the main web site] /data/aircraft/n31rx#c448407
    (sorry, I am a new member, I cannot post an actual link yet)

    My Radar Code T-KCCR8 (the account I upload with)

    Time: 7:20 AM PST / 15:20 UTC
    Registration: N31RX
    Lat: 37.9369
    Long: -122.1273
    ZIP Code: 94598 East of San Francisco

    The FR24 web site has spotty coverage of this helicopter flight as it approaches,
    flying at approximately the 1650 feet, but once it descends down into the valley, it vanishes.

    Any ideas on why this is happening / how I can get the “full picture” of these low helicopter flights?

    -- Mike


  • #2
    I suspect by the very short tracks it has that it is a MLAT target (no position details broadcast) and the feeder in your screenshot is possibly also a FA feeder and sending out mlat as ADSB tagging.

    When your receiver sees it, does it show GPS position data, or just reg, sq and altitude?

    The other thing that effects low altitude targets is patchy data. The feeder requires a solid signal for a undetermined period before being accepted as accurate and sent on. So while local display might show it and hang onto it for 10seconds waiting for next data, the feeder may decide it is not repetitive enough.
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers


    • #3
      Hi Oblivian, Thanks for all the clues in your response. There are lots of things in there for me to research this weekend, including re-configuring so that I have more detailed logs in my local software. Thanks again!


      • #4
        Most REACH helicopters are tracked by MLAT.
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