On 09/15/2011 05:15 PM, Martin Fenelon wrote: > I like to think that the positional errors of many (most non US?) > aerodromes are due to mistakes made when changing from one datum to > another.
Well, that's not what I think, based on looking at the data. The very first non-US example I looked at was ES03 "Hova" for which the apt.dat position is off by hundreds of meters, to the southeast. Nearby we have ESVF "Frolunda" for which the apt.dat location is off in another direction, and the relationship of its two runways to each other is wrong. It is hard to see how a change in datum could have a different effect on two nearby airports ... and there is just no way it could have a different effect on two runways at the same airport. There aren't that many different datums to play with. > Errors in runway orientation at unmodifed airfields (with > default layouts) appear to be caused by confusion between magnetic and > true bearings, with magnetic being used as true. Uhh, in apt.dat the runway heading for ES03 is off by more than 35 degrees. The local magnetic deviation is more like 4 degrees. Bottom line: Many of the apt.dat entries are just wrong. You don't need any ultra-sophisticated geodetic expertise to understand what is going on. The entries are just wrong. If you want something to be accurate to a few centimeters, or even a few meters, then some expertise is required, but that's not what we're talking about here. ------------------------------------------------------------------------------ BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA http://p.sf.net/sfu/rim-devcon-copy2 _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
