Richard A Downing writes: > > I'm working my way through some of the UK aerodromes, and have hit some problems > agreeing ANY of the decimal coordinates > in the FG files with the DMS coordinates given in the UK AIP. > > For instance, London Gatwick (EGKK) has ARP at N510853 W0001125, which by my > calculations comes out as > 51.148056/-000.190278. (Degrees + Minutes/60 + seconds/3600). > As it happens the ARP for EGKK is defined by the midpoint of RW 08R/27L. > > Now the FG data has Gatwick's ARP at 51.146661/-000.188750, and the midpoint of RW > 08R/27L at 51.146667/-000.188750 - > close! but not right.
!!!! WARNING !!!!! FGFS is *NOT* a navigation tool and *NOT* to be used as such However >>> from math import pi >>> SG_RAD_TO_NM = 3437.7467707849392526 >>> rads = (51.146661 - 51.146667) * pi / 180 >>> SG_NM_TO_METER = 1852.0000 >>> rads * SG_RAD_TO_NM * SG_NM_TO_METER -0.66671999989580399 or about 2 feet ! Close enough :-) Note the FlightGear Earth model makes some assumptions that may not always yield this good of a result. The assumptions and what kind of systematic errors they produce should be obvious to those that read the code and understand basic geodetics however IMHO the current system is *more* then 'good enough' for a simulator as the above demonstrates. Cheers Norman _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
