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  • Two basic questions

    Hi,

    First time poster here. I have two quite basic questions. I'm sure they've been asked/answered before but I checked the FAQ and tried searching... Anyhow:

    1. Does FR24 use some kind of positioning prediction? Often I see planes in at a certain position on the map and all of a sudden they are moved back?
    2. Secondly, I've been looking at JFK recently and I see planes in the middle of nowhere (e.g. taking off from a position quite some distance from the runway or taxing where they don't belong)

    Here's an example:

    https://dl.dropboxusercontent.com/u/28406605/off.png

    Why is that? Is it a transponder/receiver/GPS/map issue?

    Many thanks.

  • #2
    the us has both live fr24 receivers and delayed faa data. when ac are in overlapping areas of both coverage often they will appear to jump forward/back and sadly there is not a lot that can be done
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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    • #3
      Hi Breach!

      1) When an aircraft loses contact with the radar, FR24 keeps showing it on the screen for a few minutes, making the prediction with the last speed/altitude that was recieved. If during this prediction the aircraft stablishes radar contact again, it appears like a little jump(forward or backward) in the screen as the speed varies constantly during the prediction and the real position of the aircraft is different from the predicted one.

      2) I have noted the same thing here in Cordoba, Argentina with some specific registrations. For example, I have seen aircrafts landing on the taxiway instead of the runway although the radar contact is not lost. I think, and this is my opinion, that is an aircraft gps issue, but I am sure that someone can explain it better.

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      • #4
        there are no predictions made with fr24 data. appart from movements between the 8sec upload of each packet if you have "animate aircraft" enabled.

        any movements that appear as predicted data is a result of bad uploaded data or overlapping data from 2 different sources ala faa/fr receiver/f4v network

        as for map position errors, google Earth is not 100% accurate as is. and position data relies on altitude and angle of view which if it does not get plotted on a 3d terrain map will look odd on a flat map like google maps
        Last edited by Oblivian; 2013-07-13, 04:13.
        Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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        • #5
          Originally posted by Oblivian View Post
          there are no predictions made with fr24 data. appart from movements between the 8sec upload of each packet if you have "animate aircraft" enabled.

          any movements that appear as predicted data is a result of bad uploaded data or overlapping data from 2 different sources ala faa/fr receiver/f4v network

          as for map position errors, google Earth is not 100% accurate as is. and position data relies on altitude and angle of view which if it does not get plotted on a 3d terrain map will look odd on a flat map like google maps
          1) I think you'll find there are track and distance predictions made. I have 'animate aircraft' off. For an area like Walgett in northern NSW where there are no receivers (Tamworth is unfortunately gone), I always 'see' aircraft on my radar receiver departing SYD as far n/w as just short of Narrabri, some 215nm away from here. They continue on the map past Walgett, some 265nm from here with my radar assigned to them some 50nm after I've lost them. I only wish I had that range. My prayers would be answered.

          2) google maps has errors just as the older type INSS systems used on some older aircraft have errors, especially on the 'after market refits' culminating in some 'grass runway' landings and 'carpark' stops alongside airports/runways. LAX and FRA are two airports that come to mind (in the past, not sure about recently). There are also the occasional glitches in data as you say.

          Very good questions Breach, thanks.

          Regards,
          Gregg
          Last edited by fungus; 2013-07-13, 22:58.
          YSSY2/T-YSSY4 [SBS-1 Basestation w/- SSE-1090 SJ Mk2 Antenna (Thanks Delcomp) ] [Uniden UBCD996T w/- 16 element Wideband Discone VHF/UHF Antenna, and tuned 108MHz-137MHz Airband Antenna] [Trialing a home-brew 1090MHz collinear antenna]

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          • #6
            There are several older aircraft where position data does not come from GPS but is estimated/calculated with various results. Worst results comes from RJ70/RJ85/RJ100 transponder that can have up to 10 km invalid position after 1-2 hours of flight, and minor errors are also common on older Fokker, B737, B757, B767 and for sure many other older aircraft.

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            • #7
              Please, I can't understand the mechanism by which a more distant radar is what appears on my radar zone. Although in the screen of adsbscope I have a lot of near and far planes. How are prioritized active radar? Thank you!

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              • #8
                Originally posted by jumbo750 View Post
                Please, I can't understand the mechanism by which a more distant radar is what appears on my radar zone. Although in the screen of adsbscope I have a lot of near and far planes. How are prioritized active radar? Thank you!
                Sorry its taken me awhile to answer your post, but the Forum is so big i could not remember where this post was.

                Have a read of this post: http://forum.flightradar24.com/threa...ll=1#post18371
                AMS Daily Fight Information: http://schiphol.dutchplanespotters.nl/

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                • #9
                  Thank you! I was worried because my radar almost no appear, and i have a very good visibility in 270. It's a clear explanation.

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