Aircraft location not accurate on map vs. outside

[rrenderman]

Is the location of the aircraft not correct?

As you can see on the map I live where the red dot is - I have a huge airtraffic overpassing straigt above my house but all this traffic appears 6km more south and 5-6 km more to the west (ahead) then they are...

And all aircraft landing in KEF overpass the runway when landing on the map

Anyone who knows why it is not correct on the map?

This one one the map was at this moment straight above my house

[Charky]

Hello,
the position shown at the map is received by one or more sensors at the plane. This data is not changed, its simply transmitted by the transponder. The position data is uploaded to google.
at least 3 things are possible.
1. The google map does not show its correct position (might have some positioning error in itself).
2. The plane does not transmit its correct position. Reason might be different sensors (f.ex. lat/lon by GPS, alt by Altimeter). There are allowed tolerances by the size of the plane.
3. The data is uploaded usually every 10 seconds or less. The route between might be calculated by your PC if animate route is ticked.

[Anmer]

And an aircraft contrail at high altitude may appear to be directly overhead when it is many kilometers further away.

[Charky]

an example of wrong data from the plane. plane has left the airport

[Mike]

Just like Anmer wrote, a plane that appears to be right over your head on FL360 might actually be flying several kilometers away.

[Anmer]

Here's another example (using the SBS-1 and Basestation) of aircraft on approach to London Heathrow. The Continental B757 appears to be landing to the north of the approach for runway 09L. This is because the older aircraft uses Inertial Navigation and not GPS. INS becomes less accurate as the flight progresses, suffering from positional "drift".

However, BOX410 has been flown by a newer B777 which I suspect uses GPS.

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