Jim Wilson writes: > >Norman Vine <[EMAIL PROTECTED]> said: > >> Perhaps tie'ing it to the current waypoint makes sense ...... hmmm >> > >Yes, but I'd probably want to wait until I was within a few >kilometers of the "current" waypoint before switching.
or perhaps when the 'current waypoint' is closer then the the 'current tower location' >That would do the trick. We'd need that anyway if we wanted to do an >approximate model of a GPS some day. I don't understand what you mean by model a GPS Are you are using 'GPS' to mean a 'muti-function' GPS receiver ? If so most of the pieces are already in place. still need a 'cross-track error' though < untested pseudo code, off the top of my head > using normallized geocentic representation i.e. direction cosine form using geocentric latitude sgdSubVec3( dir, track_start, track_end ) // simgear function sgdClosestPointToLine( closest_pt, current_pt, track_start, dir ) // can probably skip this next step for 'short enough' tracks sgdNormalizeVec3(closest_pt) sgdScaleVec3(closest_pt,sea_level_radius) sgdScaleVec3(current_pt, sea_level_radius) sgdSubVec3(error_vec, closest_pt, current_pt) // this should be close enough for our purposes crosstrack_error_dist = sgdScalarProductVec3(error_vec) Norman _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel