On Mon, 21 Oct 2002 21:03:18 -0400, <[EMAIL PROTECTED]> wrote in message <[EMAIL PROTECTED]>:
> Andy Ross writes: > > > > An excellent point -- I wonder how they do it, then? On the > > > ground, they can obviously line up with something well known, and > > > in VFR, they can line up two landmarks on the map, but how to > > > update the DG in IFR? > > > > As Alex points out, if you have three receivers (and synchronize > > them to use the same satellite set) you can get the location for > > each point of a triangle and figure out the orientation for that. > > Right, but I'm not asking how people could do it but how they actually > do. I doubt that most pilots in the north have 3-GPS in-flight setups > right now. ..standard is "one antenna for vfr type flight", position is accurate within a 300ft diameter by 450 ft tall "error egg" with cold war type crypto turned on, egg shrinks to 35?ft by 50?ft on turning off the crypto (random noise vector) signal. The "error egg" shrinks further when additional observations are added to the equation set, such as altimeter, DG, GS etc readings, exact position of antenna(s) and other sensors on airframe, in relation to its datum origo. Differential GPS may add one or more ground station "satellite" observations to the equation set, the early work tried to calculate and nullify the random noise vector, and instead added (athmosphaerically bent) signal path leg errors. ..AFAIK, the average aviator "up north" uses cheap shelf ware gps units "to back up" his nav work. ;-) -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
