On Monday 12 September 2005 00:20, Steve Knoblock wrote: > The Digitrak autopilot project is coming along. I have the first mode > running, which captures and holds the GPS track. I get the GPS heading > to feed to the autopilot controller from the default GPS instrument. > The autopilot is set to reduce the GPS bug error to zero by driving > the aileron until the orientation roll equals the target roll. This > works fine, however, I notice some differences in the numbers reported > by the heading and track properties.
Are you sure that the Digitrack actually knows the roll angle of the airplane? > I may be a dummy, but can anyone explain this? Not the variation > between true and magnetic, but between GPS and orientation. Heading and track are _not_ the same thing. Heading is the direction that the nose of the aircraft is pointing. Track is the direction that the aircraft is moving. You probably have a crosswind that is blowing your aircraft to one side. The numbers that you observe seem quite reasonable. If you try to fly parallell to the wind, heading and track should be similar. For a good explanation of the different GPS navigation terms read chapter 7 of John Bell's "Cockpit GPS" available on-line http://www.cockpitgps.com -- Roy Vegard Ovesen _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
