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Author Topic: 777's not tracking correctly  (Read 8031 times)

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GreekSpy2001

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777's not tracking correctly
« on: September 09, 2009, 09:54:56 AM »
I see that many 777s are being tracked on the map but give the circle location id rather that the airplane.  I know, we'll understand maybe,  that this is because the heading can't be determined, but it seems the 777 is a major culprit.  today I have had this from 777s operated bu DL UA BA and Air INdia.  This regular happens with 777s. Anyone know why this is peculiar to 777s?

Graham

tarbat

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Re: 777's not tracking correctly
« Reply #1 on: September 09, 2009, 10:10:51 AM »
And why not all B777s?  Is it just particular airlines - these Air France and American ones seems to have a heading okay.

« Last Edit: September 09, 2009, 10:17:56 AM by tarbat »

DaveReid

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Re: 777's not tracking correctly
« Reply #2 on: September 09, 2009, 10:32:30 AM »
I see that many 777s are being tracked on the map but give the circle location id rather that the airplane.  I know, we'll understand maybe,  that this is because the heading can't be determined, but it seems the 777 is a major culprit.  today I have had this from 777s operated bu DL UA BA and Air INdia.  This regular happens with 777s. Anyone know why this is peculiar to 777s?

AFAIK, all 777s send either heading or track (or both).  I don't understand why RadarBox can't use whichever one is sent to orient the aircraft symbol.

In fact, I'm sure we've covered this before.
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tarbat

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Re: 777's not tracking correctly
« Reply #3 on: September 09, 2009, 10:37:31 AM »
AFAIK, all 777s send either heading or track (or both).  I don't understand why RadarBox can't use whichever one is sent to orient the aircraft symbol.

Dave, is this a simple case of Radarbox needing to decode another ModeS frame?  If so, have you got details that maybe Airnav can implement?

DaveReid

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Re: 777's not tracking correctly
« Reply #4 on: September 09, 2009, 10:54:53 AM »
Dave, is this a simple case of Radarbox needing to decode another ModeS frame?  If so, have you got details that maybe Airnav can implement?

No, RadarBox already decodes the DF17 (Extended Squitter) Format Type Code 19 (Airspeed and Heading) Subtype 3.

That's where the TAS values that you sometime see displayed are coming from (though RadarBox incorrectly labels them as IAS).
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Fenris

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Re: 777's not tracking correctly
« Reply #5 on: September 09, 2009, 10:57:06 AM »
Dave, is this a simple case of Radarbox needing to decode another ModeS frame?  If so, have you got details that maybe Airnav can implement?

No, RadarBox already decodes the DF17 (Extended Squitter) Format Type Code 19 (Airspeed and Heading) Subtype 3.

That's where the TAS values that you sometime see displayed are coming from (though RadarBox incorrectly labels them as IAS).

And wasn't that last thing one of the bugs to be fixed for the new version? Has it been or is it still extant?

DaveReid

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Re: 777's not tracking correctly
« Reply #6 on: September 09, 2009, 11:10:04 AM »
That's where the TAS values that you sometime see displayed are coming from (though RadarBox incorrectly labels them as IAS).

And wasn't that last thing one of the bugs to be fixed for the new version? Has it been or is it still extant?

Nope, the column is still labelled IAS in V3.02 - I notice from time to time aircraft apparently flying around at airspeeds that should tear their wings off.

Perhaps AirNav need to hire a pilot to explain the difference between IAS and TAS to them.  Oh, hang on though ...

Sorry, Andre - you know I'm only teasing !    :-)
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Fenris

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Re: 777's not tracking correctly
« Reply #7 on: September 09, 2009, 11:27:46 AM »
That's where the TAS values that you sometime see displayed are coming from (though RadarBox incorrectly labels them as IAS).

And wasn't that last thing one of the bugs to be fixed for the new version? Has it been or is it still extant?

Nope, the column is still labelled IAS in V3.02 - I notice from time to time aircraft apparently flying around at airspeeds that should tear their wings off.

I thought that the problem was that some aircraft do provide IAS, so what's needed is a second column and the appropriate value to be placed in the relevant one for each aircraft.

Like you I have seen numbers well in excess of Vne!

I always find it strange seeing TAS values above 250kt for aircraft below 10,000 feet, I'd much rather see IAS if only it were widely available.

DaveReid

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Re: 777's not tracking correctly
« Reply #8 on: September 09, 2009, 11:42:43 AM »
I thought that the problem was that some aircraft do provide IAS, so what's needed is a second column and the appropriate value to be placed in the relevant one for each aircraft.

In theory, yes,  That's to say that there is provision in the Mode S spec for a flag in the Airspeed/Heading Squitter to indicate whether the airspeed value being sent is IAS or TAS.

Having said that, back in November I analysed nearly 140,000 Airspeed/Heading Squitters from 97 different aircraft and not a single one contained IAS.  So changing the column heading from IAS to TAS would seem a safe and sensible thing to do.
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GreekSpy2001

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Re: 777's not tracking correctly
« Reply #9 on: September 09, 2009, 11:55:32 AM »
So my question is why do I see this with 777's .  Enough times to notice it and not really notived with other types.  Will post a jpg when it happens again....

Graham

GreekSpy2001

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Re: 777's not tracking correctly
« Reply #10 on: September 09, 2009, 12:01:49 PM »
Ok just as I lasted posted 777 SU-GBY was displaying this phenomenum.

See attached screen shot

Graham

DaveReid

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Re: 777's not tracking correctly
« Reply #11 on: September 09, 2009, 12:07:15 PM »
So my question is why do I see this with 777's .  Enough times to notice it and not really notived with other types.

If you mean why don't you see an aircraft symbol for many 777s, it's because RadarBox doesn't make use of heading data that it decodes, only track data.

If you mean why do those particular aircraft send heading and not track, I have no idea  :-)
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GreekSpy2001

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Re: 777's not tracking correctly
« Reply #12 on: September 09, 2009, 12:24:23 PM »
Interesting that in my experience it is only 777s that send heading and not track and produce this on my screen.  And as Tarbat has shown it is not all 777s.  Maybe a discrepancy in install/config of the equipment on the prod line at Paine/Everett.  Maybe the 787 whenever it flies will be the same, same prod line.  

But then ARNB V10.0.1 will be out by then and it may take notice the heading info ;-)

Oh well thanks all

Graham

Fenris

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Re: 777's not tracking correctly
« Reply #13 on: September 09, 2009, 12:25:57 PM »
So my question is why do I see this with 777's .  Enough times to notice it and not really notived with other types.

If you mean why don't you see an aircraft symbol for many 777s, it's because RadarBox doesn't make use of heading data that it decodes, only track data.

If you mean why do those particular aircraft send heading and not track, I have no idea  :-)

I'm wondering if there is a subtle bug somewhere related to this.

I've seen a couple of cases, I think with either UAL or AAL aircraft, where initially I see a track with the aircraft symbol pointing where it should.Then, because of the topography around my house, the track times out and the symbol changes to the circle with x inside it. Before the final timeout occurs to remove the symbol from the map, reception returns and the track reappears. The aircraft is still transmitting the same ADS-B frames, but from that point on the circle with x symbol remains until I lose coverage completely.

It's certainly very infrequent, I've seen it twice now that I can be sure about.