On Mon, 2005-06-20 at 16:29, Roberto Inzerillo wrote:
> Hi,
>  I have an aerial picture of airport LICP (Boccadifalco, Italy) with UTM33N
> coordinates  [...] as soon as I overlap it to the scenery data in FGSD, I have
> it displaced by by approximately 550m.
> 

550m? That's a big error!

FlightGear uses WGS84 coordinates, but I'd not expect such a big
deviation between WGS84 and any other geodesic system.

Proving FlightGear's dataset is easy if you have a GPS receiver. Go
stand on some part of the airport that has a reference point in
FlightGear's data file. (The touchdown point on the main runway for
instance... :-))


See what your GPS receiver says the coordinates are. The GPS reading
should not be out by more than a few metres if you've got a good signal.

Then, scrape yourself off the wheels of the Jumbo Jet that just landed
on your head, and tell everyone if the FlightGear data is good or not.

If UTM33N really is 550m displaced from WGS84 at that location, you can
probably still use the UTM33N data if you offset it by the right amount.
You may have to rotate it a bit too. Over such a small area, any ground
distances you measure will be the same in both systems after simple
correction.

Steve


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