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. So, following this concept, you could implement this in Nasal by using the following algorithm: 1) implement a data type for holding the velocity and simulation-time for the current frame. Then, push the instance of the data type into a queue every frame. (The queue can be found here http://cvs.flightgear.org/cgi-bin/viewvc/viewvc.cgi/data/Aircraft/A380/Systems/FDX/Switch/queue.nas?revision=1.1&view=markup) 2) Go through the queue and dequeue instances that are X seconds old. Then, calculate the delta_t between two instances and multiple the value by the acceleration in one of the instances. 3) Summing up all the results in step 2 and dividing the result by X should give you the ground speed. I hope this helps. :D Ampere ------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-devel
