> On Wednesday 30 May 2007 21:53, syd & sandy wrote: > > Hi Jon , thanks for the reply , I'm not sure I know WHAT I'm > doing anymore > > :) I wanted to output groundspeed to a property in > /velocities/, in knots, > > so that it would be available for instruments... rather than having it > > redone in Nasal ... but nasal is beginning to look more inviting at the > > moment ... > > > > and I just discovered I cant "return gspd" .... > > Its probably a simple matter for the gurus , which I'm definately not ! > > > > cheers, > > Syd > > Hello Syd, > > If I were to build an instrument on an actual aircraft for > measuring ground speed, I would use an accelerometer and integrate its output.
That's a good observation. The ground speed coming out of JSBSim is the environment ground speed, which is effectively a "perfect sensor". In JSBSim one could define a simulated sensor in the flight control section of the configuration file as follows (the name of the component is somewhat arbitrary): <sensor name="sensor/velocities/groundspeed-fps"> <input> velocities/vg-fps </input> <lag> 0.5 </lag> <noise variation="PERCENT"> 2 </noise> <bias> 0.5 </bias> </sensor> This will give a property "sensor/velocities/groundspeed-fps" (which would probably have the fdm/jsbsim/ prefix) that is a lagged environment ground speed with some noise in it of amplitude 2% of the value, and a bias of 0.5 ft/sec. You could also add a drift rate in the signal by using the <drift_rate> element. If you wanted the signal in kts you could put a gain in the command path before the sensor. The above may well be more than you want to do, but I thought I'd mention an approach that could be used in JSBSim aircraft. Jon -- Jon S. Berndt Development Coordinator JSBSim Project www.JSBSim.org ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
