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Thread: Aircraft Movement Not Viewable at Some Airports

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    Aircraft Movement Not Viewable at Some Airports

    Why is it that for some airports, such as SEA, we can view in Flightradar24 the movement of aircraft on the ground, while at other airports (such as PVG) is the view apparently blocked and departing aircraft are not viewable until the aircraft reach approx. 3,500 feet?

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    Quote Originally Posted by KAK View Post
    Why is it that for some airports, such as SEA, we can view in Flightradar24 the movement of aircraft on the ground, while at other airports (such as PVG) is the view apparently blocked and departing aircraft are not viewable until the aircraft reach approx. 3,500 feet?
    Because it is dependant on if there is a receiver nearby.

    ADSB = Line of sight. No sight, no coverage.

    Ground-sky = no obstacles

    ground-ground = obstacles


    3000ft is also near FR24 min height for MLAT (non GPS position transmitting) aircraft. So anything below can't be calculated if this type of transmitter
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    Quote Originally Posted by Oblivian View Post
    Because it is dependant on if there is a receiver nearby.

    ADSB = Line of sight. No sight, no coverage.

    Ground-sky = no obstacles

    ground-ground = obstacles


    3000ft is also near FR24 min height for MLAT (non GPS position transmitting) aircraft. So anything below can't be calculated if this type of transmitter
    Thanks, Oblivian. I should have mentioned that aircraft ground movement used to be viewable at PVG but is no longer. Curious if there's some kind of blocking of the signals; also, DCA has never been viewable at least for the time that I've been on FR24. I would expect that DCA would have some ADSB coverage. I guess my question is really one of whether (and how) ADSB signals can be blocked such as for security reasons?

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    They can't for certain zones. Your receiver either covers an area, or it doesn't

    I'm sure we would hear more squawking if the map had any hidden zones the feeders know are being uploaded.

    But feeders can come and go (or break and not be fixed)
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    Quote Originally Posted by Oblivian View Post
    They can't for certain zones. Your receiver either covers an area, or it doesn't

    I'm sure we would hear more squawking if the map had any hidden zones the feeders know are being uploaded.

    But feeders can come and go (or break and not be fixed)

    Okey dokey. Thanks for the quick reply, Oblivian.

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    In short, coverage is mainly up to people making sure ground areas are densly deployed.

    And if FR is blocking any, they sure won't admit it!
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  7. #7
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    I think there is just no feeder at DCA.
    But there are webcams on youtube with some nice views of DCA

    As for PVG, there have been problems for people in China feeding FR24 according to a thread some time ago.
    The number of feeders has reduced significantly i believe.

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