On Thu, 1 Feb 2007, George Patterson wrote:

> The interpolation should also take into account the distance between the
> METAR stations and the plane and weight the effect of the weather
> effects from there.
>
> Example: If I am flying right above a METAR station and there is another
> one 100km away, then ignore the distant station.

Well it is ignored already of course. ;) At the moment, only the nearest
METAR is used. The other idea (other than time interpolation) is to compute
some sort of weighed average between METAR stations around the aircraft
depending on the distance to them.

Time interpolation is necessary too anyway, to smoothen out a METAR update from
the one and same station, and also for transients emanating from switching the 
set of
stations being used as lined out above. I would expect these changes to be
fairly small under normal circumstances (although a front can pass a
station and shift the wind quite dramatically)-- but it's still transients
and can stir up autopilots.

But I think I have ran into a bug too:
Using --enable-real-weather-fetch does not set
/environment/weather-scenario to "METAR" automatically. The environment
code checks that property here and there, so I guess it matters.

METAR is not an optimal source for weather data, but perhaps the best
we can get for now (without paying big money for it). There are no METAR
stations out in the oceans for instance. And all METAR stations does not
provide the same set of information either. An alternative to using METAR
could be designing some sort of weather generator server that provides a
realistic (not real) weather which, contrary to METAR, has complete data for
the whole world.

I have something now which is a fair bit better than it was before:
notoriously barrel rolling the pa24-250 on a METAR switch has been replaced
by a mere shake. (I have yet to figure out what @$&*%! piece of code is
bypassing my nice and smooth interpolation of
/environment/pressure-sea-level-inhg all the time.)

-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier.
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Flightgear-devel mailing list
Flightgear-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/flightgear-devel

Reply via email to