Re: [Flightgear-devel] Speed discontinuity
On Wed, 2006-04-19 at 21:20 -0600, Ron Jensen wrote: The approach to my favorite airport (KHIF runway 14) passes over another airport (KODG) with metar weather. As a result I almost always see a major weather shift on very short final. Ron Hi Ron, I can see why you like the airport. The terrain around KHIF is superb. :-) Regards George --- 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=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Speed discontinuity
On Wed, 2006-04-19 at 21:20 -0600, Ron Jensen wrote: On Tue, 2006-04-18 at 20:14 -0400, Ampere K. Hardraade wrote: On Wednesday 19 April 2006 01:21, John Wojnaroski wrote: A change that large (13 knots!!) is a major wind shear. Might it make sense to provide some sort of filtering or extrapolation between stations to moderate such extreme changes Regards John W. I also find it extremely annoying. This also relates to the why does my aircraft jerk suddenly question that we get occasionly. Some people like to think that it is some sort of turbulence, but the not-very-well-thought-out weather simulation routine is the most likely suspect. As John said, instead of relying on just one set of data from a single station, it might make sense to take data from all the surrounding stations and perform some extrapolation. Ampere Or perhaps perform an interpolation over several seconds when updating/changing the weather? The approach to my favorite airport (KHIF runway 14) passes over another airport (KODG) with metar weather. As a result I almost always see a major weather shift on very short final. Ron I have captured the metar strings when I fly from the default runway from KHIF passing over KODG (as a guess). Total flighttime was only a matter or minutes in a b1900d. 2006/04/24 17:55 KHIF 241755Z 07014G22KT 7SM FEW030 BKN060 BKN100 08/M02 A2996 RMK SLP133 ALSTG ESTMD SLP ESTMD WR// P DRY 51003 2006/04/24 17:53 KOGD 241753Z 33005KT 10SM SCT050 09/01 A3000 RMK AO2 RAB1655E04 SLP139 P 60001 T00940011 10100 20056 51013 2006/04/24 17:55 KHIF 241755Z 07014G22KT 7SM FEW030 BKN060 BKN100 08/M02 A2996 RMK SLP133 ALSTG ESTMD SLP ESTMD WR// P DRY 51003 The weather changes were very sudden with the aircraft jerking as the plane cross weather zone boundaries. Regards George --- 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=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Speed discontinuity
John Wojnaroski wrote: A change that large (13 knots!!) is a major wind shear. Might it make sense to provide some sort of filtering or extrapolation between stations to moderate such extreme changes Indeed - but remember, that interpolation between different METAR stations does not only affect wind. Cloud layers, pressure, visibility and other environmental effects are related. How do you handle AI/MultiPlayer setups ? Different scenarios arise: a) You travel from the vincinity of one METAR station to another and b) all METAR stations get an update - which probably has a _huge_ effect in the morning. To handle all these different tasks might result in a large overhaul of the weather subsystem and I believe this is the reason why nobody took a stab at it yet. Still I confess that I would consider only partial improvement as a great deal !!! Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- --- 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=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Speed discontinuity
On Wednesday 19 April 2006 01:21, John Wojnaroski wrote: A change that large (13 knots!!) is a major wind shear. Might it make sense to provide some sort of filtering or extrapolation between stations to moderate such extreme changes Regards John W. I also find it extremely annoying. This also relates to the why does my aircraft jerk suddenly question that we get occasionly. Some people like to think that it is some sort of turbulence, but the not-very-well-thought-out weather simulation routine is the most likely suspect. As John said, instead of relying on just one set of data from a single station, it might make sense to take data from all the surrounding stations and perform some extrapolation. Ampere --- 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=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Speed discontinuity
John Wojnaroski wrote:
Curtis L. Olson wrote:
John Wojnaroski wrote:
There will be some slight hesitations when new tiles are loaded.
It's possible that a large dt could cause you to overshoot your
target. If you factor dt into your control algorithm (if it's not
already) that might help? I'd take a close look and see if dt spikes
at the same time as your anomolies.
Okay, here is the point of the discontinuity. This is data on the FG
side that is being sent to the sim
code snippets
setting up the property pointers
p_altitude_agl(fgGetNode(/position/altitude-agl-ft, true)),
vel_kcas(fgGetNode(/velocities/airspeed-kt[0], true)),
and then packing the data into the UDP packet and a temp file to save it
data-v_kcas = vel_kcas-getDoubleValue();
// speed_buf[s++] = vel_kcas-getDoubleValue();
fprintf( speed, %5d %f\n, s++, vel_kcas-getDoubleValue() );
cout s data-v_kcas endl;
if ( s 1 ) {
s = 0;
fclose( speed );
speed = fopen( velocity , w );
}
.
and the point of the speed change (first number is just a frame
counter for reference)
2874 249.876
2875 249.877
2876 249.876
2877 249.876
2878 249.877
2879 249.876
Altitude = 60
Temp at alt (C) = 17
Temp sea level (C) = 17.118
Altitude = 60
Dewpoint at alt (C) = 7
Dewpoint at sea level (C) = 7.012
2880 262.848
2881 262.848
2882 262.845
2883 262.841
2884 262.837
2885 262.833
2886 262.825
2887 262.822
Again, this is happening in FG. The intervening data is from the
terminal at the point of the speed change and I assume this has
something to do regards the tile data.
Any ideas, suggestions as to what is happening to cause the speed
change. Might it be related to altitude, except the baro altitude is
not changing. My hunch it is somehow related to fetching real world
weather and atmospheric weather data not propagating to the new tile.
With weather fetching turned off the problem goes away in that the
baro setting is set to standard 29.92/1013 while with real weather the
baro setting was 30.01
That output is from the real time weather fetcher. If the winds change
when new weather is fetched, that could account for an instantaneous
speed change (relative to the local airmass.)
Curt.
--
Curtis Olsonhttp://www.flightgear.org/~curt
HumanFIRST Program http://www.humanfirst.umn.edu/
FlightGear Project http://www.flightgear.org
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