Re: [Flightgear-devel] Heading on NMEA

[Adam D. <ade...@ex...>]

On May 7, 2007, at 3:32 PM, Curtis Olson wrote:

> On 5/7/07, Adam Dershowitz wrote:
> I have dug into this a little further and found something odd.
> I found that the NMEA data is driven by /velocities/speed-east-fps
> and /velocities/speed-north-fps.  So I calculated these and added
> them to my csv data file, and the playback config file.  The oddity
> is that even though my file now has them, these values are not
> changing in FG.  They remain 0.  I am using the null FDM and a the
> generic protocol, and all else seems to be working correctly, except
> on the NMEA data, that is used by Atlas among other things, the
> heading and speed are showing as zero.
> Any ideas why I can't get the generic protocol to change these two
> velocities when it can change other values just fine?
>
> I don't recall about this specific set of properties, but you have  
> to be careful ... some fdm properties are derived from other  
> properties and auto calculated.  I believe that most of the logic  
> for what is computed from what can be found in src/fdm/flight.[ch]xx
>
> This code traces back to some of the earliest days of FlightGear so  
> it's a bit clunky in spots, but it works.
>
> Regards,
>
> Curt.
> -- 
>

Curt,

I tried digging in the code some.  I then did an interesting test.  I  
just tried hand flying while recording data using the included  
playback.xml:
--generic=file,out,1,FG_test1.csv,playback
then playing it back with this:
--generic=file,in,1,FG_test1.csv,playback  --fdm=null

The odd thing is that given this xml that seems to record most of the  
data, when I playback the data /velocities/speed-east-fps remains  
0.0.  So it does seem like there is a bug.

Any ideas?