jfjk
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 10:14 am

I often track BA780 on flightradar24 and most often it is "landing" to the north east of the active runway in Arlanda. I believed that Flightradar used possitioning from the aircrafts but cannot understand why they then are wrongly possitioned compared to the active runway. It dosen't seem to happen with most other flights.

Can anyone shed some light on this?

Moderators if this is the wrong forum for such a question pls. move
 
kl911
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 10:47 am

Quoting jfjk (Thread starter):
I often track BA780 on flightradar24 and most often it is "landing" to the north east of the active runway in Arlanda. I believed that Flightradar used possitioning from the aircrafts but cannot understand why they then are wrongly possitioned compared to the active runway. It dosen't seem to happen with most other flights.

Can anyone shed some light on this?

Moderators if this is the wrong forum for such a question pls. move

The BA flight at ATH has the same problem while others land direct on the runway. I think it has to do with BA, maybe anti terror or something.

edit: On 2nd thought, is ARN also flown with a 767 like ATH? Then it might have to do with the 767 transponder.

[Edited 2014-10-25 04:06:46]
 
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blooBirdie
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 11:22 am

Quoting kl911 (Reply 1):
edit: On 2nd thought, is ARN also flown with a 767 like ATH? Then it might have to do with the 767 transponder.

I've noticed this with older aircraft where the transponder has been retrofitted. It applies to a slightly lesser degree with BA's 744s. (They line up on the runway OK, but when they're taxiing they're usually stuck at 5 or 8 degrees, which can sometimes make it look as if they're taxiing backwards.)
 
aviatorcraig
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 11:22 am

I don't think this is specific to BA, but some aircraft appear regularly to show up incorrectly.

One of the last flights out of LHR every night at around 11.15pm is a DHL A300. When this aircraft is taxiing to the threshold of 27R, Flightradar24 shows it taxiing through the town of Harlington approx 1 km north of the airfield boundary!

Sorry, I haven't got a clue why.
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kl911
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 11:24 am

Quoting aviatorcraig (Reply 3):
One of the last flights out of LHR every night at around 11.15pm is a DHL A300. When this aircraft is taxiing to the threshold of 27R, Flightradar24 shows it taxiing through the town of Harlington approx 1 km north of the airfield boundary!

Must be great to live in Harlington..    
 
Koosi
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 12:04 pm

Did you check the FAQ section of the FR24 website? I'm pretty sure the answer is there under "Why did it look like the aircraft landed outside the runway? Has it crashed?"
http://www.flightradar24.com/faq
 
gordonsmall
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 12:05 pm

Quoting kl911 (Reply 1):
On 2nd thought, is ARN also flown with a 767 like ATH? Then it might have to do with the 767 transponder.

It is. BA 767's are not equipped with ADS-B out, therefore FR24 will be using multilateration to estimate the position based on the Mode S transponder output which has little or no accuracy.
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flyingbird
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 7:42 pm

Quoting Gordonsmall (Reply 6):

It is. BA 767's are not equipped with ADS-B out, therefore FR24 will be using multilateration to estimate the position based on the Mode S transponder output which has little or no accuracy.

MLAT have same accuracy as ADS-B or better. The answer to the question can be found in the FAQ (as written 2 posts up) http://www.flightradar24.com/faq
 
gordonsmall
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Wrong Positioning In Flightradar24

Sat Oct 25, 2014 9:41 pm

Quoting flyingbird (Reply 7):
MLAT have same accuracy as ADS-B or better.

Have a word with yourself boy. ADS-B Out position reporting is based on GPS co-ordinates which are extremely accurate, multilateration is based on pure guesswork derived from low-frequency updates of trajectory and groundspeed. It is not mathematically possible for the two to have similar accuracy without some serious coincedence.
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EA CO AS
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Wrong Positioning In Flightradar24

Sun Oct 26, 2014 1:26 am

Isn't there a 5 minute lag on all data though?
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Comments made here are my own and are not intended to represent the official position of Alaska Air Group
 
flyingbird
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 6:35 am

Quoting Gordonsmall (Reply 8):
ave a word with yourself boy. ADS-B Out position reporting is based on GPS co-ordinates which are extremely accurate, multilateration is based on pure guesswork derived from low-frequency updates of trajectory and groundspeed. It is not mathematically possible for the two to have similar accuracy without some serious coincedence.

I guess you should read about Multilatiraion. MLAT has nothing to do with guessing, it's pure Mathematics. The ModeS transponder sends out a ping. And with MLAT you are calculating with mathematics the position of this ping. With good receivers and good formulas you can get the position with an accuracy of less than a meter.

ATC around Europe are using MLAT to track ADS-B aircraft as the MLAT data actually is more accurate than ADS-B.
 
flyingbird
Posts: 139
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 6:39 am

Quoting EA CO AS (Reply 9):

Isn't there a 5 minute lag on all data though?

Why is this thread full of guessing and speculations when all information can be found on Flightradar24 web page?

Please read http://www.flightradar24.com/how-it-works and http://www.flightradar24.com/faq before posting incorrect speculations.
 
gordonsmall
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 12:23 pm

Quoting flyingbird (Reply 10):
I guess you should read about Multilatiraion. MLAT has nothing to do with guessing, it's pure Mathematics. The ModeS transponder sends out a ping. And with MLAT you are calculating with mathematics the position of this ping. With good receivers and good formulas you can get the position with an accuracy of less than a meter.

The calculus used to derive the positions may be pure mathematics, but the Mode S updates are based on analogue signals which can be affected by all sorts of external factors. TCAS is based on these same calculations using the same data and is equally innacurate, even at close range. I've lost count of the number of times a TCAS targeyt has not been where I expect it to be based on the data displayed.

I have no doubt that the mathematics are very accurate, but if the data being fed into the calculations is innacurate then the output is going to be innacurate by an equal or greater margin.. Garbage in = Garbage out.

Quoting flyingbird (Reply 10):
ATC around Europe are using MLAT to track ADS-B aircraft as the MLAT data actually is more accurate than ADS-B.

I think you'll find they use multilateration derived from the ADS-B data to predict position, MLAT is simply a mathematical method of prediction a trajectory based on trend data, it is NOT the data itself. Also, ADS-B Out transmits the ACTUAL aircraft position based on an Intertial, Ground Nav and GPS position mix, how can it be any more accurate than that? Have you actually read what you're typing?
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Vasu
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 1:31 pm

Some of the 757 flights into/out of LGW do this too. I always seem to see G-MONK, G-JMAA, G-JMAB etc landing in fields south of the airport!
 
flyingbird
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 3:35 pm

Quoting Gordonsmall (Reply 12):
The calculus used to derive the positions may be pure mathematics, but the Mode S updates are based on analogue signals which can be affected by all sorts of external factors. TCAS is based on these same calculations using the same data and is equally innacurate, even at close range. I've lost count of the number of times a TCAS targeyt has not been where I expect it to be based on the data displayed.

I have no doubt that the mathematics are very accurate, but if the data being fed into the calculations is innacurate then the output is going to be innacurate by an equal or greater margin.. Garbage in = Garbage out.

I think you'll find they use multilateration derived from the ADS-B data to predict position, MLAT is simply a mathematical method of prediction a trajectory based on trend data, it is NOT the data itself. Also, ADS-B Out transmits the ACTUAL aircraft position based on an Intertial, Ground Nav and GPS position mix, how can it be any more accurate than that? Have you actually read what you're typing?

Sorry, but you don't understand how MLAT works. MLAT have nothing to do with prediction or trend data. You must have confused MLAT with something else.

No ADS-B does not transmit the ACTUAL aircraft position. ADS-B was designed to transmit the ACTUAL position but reality shows that any garbage can be sent out. FAA calculations shows that 37% of ADS-B installations in USA are sending out some of data ADS-B incorrect.

http://www.recreationalflying.com/th...ng-top-issues-for-aviation.116149/

Quote:
During ADS-B sessions at the AEA show, FAA officials revealed there have been problems with some installations, as measured by the FAA’s ADS-B Compliance Monitor system. About 754 of the aircraft 2,034 aircraft equipped for 1090ES ADS-B out (for flights above FL180) and 94 of the 1,106 aircraft equipped for 978UAT are sending inaccurateADS-B out position, velocity and time information to the ADS-B ground infrastructure.

MLAT calculates the position of the transmitter/signal, no matter what the transmitter is transmitting! The ModeS transmitter can be sending out any garbage and MLAT will triangulate this source of the signal and calculate the position with accuracy of less than one meter.

That is why MLAT is better than ADS-B! With ADS-B you are dependent of the aircraft sending correct position and as this threads and FAA numbers shows, there are many aircraft sending out wrong position. With MLAT you always get 100% correct position if you do the maths correct. European ATC MLAT is often done with 12+ receivers which assures very accurate data quality. FR24 is using 4+ receivers to calculate MLAT positions.

[Edited 2014-10-26 08:45:22]
 
flyingbird
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 3:58 pm

Quoting Gordonsmall (Reply 12):
The calculus used to derive the positions may be pure mathematics, but the Mode S updates are based on analogue signals which can be affected by all sorts of external factors. TCAS is based on these same calculations using the same data and is equally innacurate, even at close range. I've lost count of the number of times a TCAS targeyt has not been where I expect it to be based on the data displayed.

I have no doubt that the mathematics are very accurate, but if the data being fed into the calculations is innacurate then the output is going to be innacurate by an equal or greater margin.. Garbage in = Garbage out.

I think you'll find they use multilateration derived from the ADS-B data to predict position, MLAT is simply a mathematical method of prediction a trajectory based on trend data, it is NOT the data itself. Also, ADS-B Out transmits the ACTUAL aircraft position based on an Intertial, Ground Nav and GPS position mix, how can it be any more accurate than that? Have you actually read what you're typing?
http://en.wikipedia.org/wiki/Multilateration

Quote:
Multilateration (MLAT) is a navigation technique based on the measurement of the difference in distance to two stations at known locations that broadcast signals at known times. Unlike measurements of absolute distance or angle, measuring the difference in distance between two stations results in an infinite number of locations that satisfy the measurement. When these possible locations are plotted, they form a hyperbolic curve. To locate the exact location along that curve, multilateration relies on multiple measurements: a second measurement taken to a different pair of stations will produce a second curve, which intersects with the first. When the two curves are compared, a small number of possible locations are revealed, producing a "fix".

Multilateration is, in general, far more accurate for locating an object than sparse approaches such as trilateration, where with planar problems just three distances are known and computed.

Example applications
GPS – Worldwide navigation system using TDOA of signals from multiple synchronised satellite-based transmitters

The GPS position that you see in your GPS unit is actually an MLAT calculation. So if you claim that MLAT is bad quality, you at the same time claim that GPS is bad quality.

MLAT can be used to localize any transmitter, not just and a ModeS transponder. You can for example calculate the position of a FM radio receiver and you will get the same position no matter if they play garbage music or not.
 
jox
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 4:22 pm

Quoting flyingbird (Reply 15):
You can for example calculate the position of a FM radio receiver

I assume you mean *transmitter*?
 
gordonsmall
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 4:24 pm

You've just ignored everything I wrote, restated some of it in your own words and then portrayed blatantly inaccurate opinion as fact.

No point in debating any further.
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flyingbird
Posts: 139
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RE: Wrong Positioning In Flightradar24

Sun Oct 26, 2014 7:33 pm

Quoting Gordonsmall (Reply 17):
You've just ignored everything I wrote, restated some of it in your own words and then portrayed blatantly inaccurate opinion as fact.

The problem is that you can't accept the fact that it's possible to calculate a better position of the aircraft than a GPS can provide. But you can't compare apples with pears. A policeman can measure the speed of a car with broken speedometer and MLAT can calculate better position of an aircraft than the onboard GPS.

Quote:
TCAS is based on these same calculations using the same data and is equally innacurate, even at close range.

No TCAS and MLAT has nothing to do with each other and there is absolutely nothing in common between TCAS and MLAT. TCAS is done with ONE receiver. MLAT NEEDS 3-4+ receivers in order to work. You are use words like "TCAS", "prediction" or "trend data" to describe MLAT. None of these words can be found on http://en.wikipedia.org/wiki/Multilateration so you have completely messed up MLAT with something else.

If MLAT is so inaccurate as you claim how come ATC claims is accurate and use it to track aircraft?
http://www.ainonline.com/aviation-ne...blishing-itself-radars-replacement

Quote:
MLat is an extraordinarily flexible and highly accurate controller tool enjoying growing installation numbers every year.



You can't get the position of a GPS receiver with one GPS satellite. In order to get a GPS position you need signal from 3-4+ GPS satellites. That gives an accuracy of about 1-5 meters. More satellites gives better accuracy. MLAT works the same way. You can't make MLAT work with one ModeS receiver. You need 3-4+ ModeS receivers in order to get 1-5 meter accuracy of the ModeS signal source. More receivers gives better accuracy. The content of the ModeS signal is never a parameter of the quality, because MLAT is calculating the position and not the content of the signal.

I was in the team building the MLAT module for FR24. So if you claim that everything that I write and ATC use is inaccurate I wonder what MLAT experience you have to come up with?

[Edited 2014-10-26 12:36:08]
 
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EA CO AS
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RE: Wrong Positioning In Flightradar24

Mon Oct 27, 2014 7:16 am

Quoting flyingbird (Reply 11):
Quoting EA CO AS (Reply 9):
Isn't there a 5 minute lag on all data though?
Why is this thread full of guessing and speculations when all information can be found on Flightradar24 web page?

Please read http://www.flightradar24.com/how-it-works and http://www.flightradar24.com/faq before posting incorrect speculations.

Pardon me for misreading, oh great and powerful maker of all things FR related.    Your FAQ points out that some FAA data has a 5 minute delay however. You could have simply pointed that out instead of being snarky.
"In this present crisis, government is not the solution to our problem - government IS the problem." - Ronald Reagan

Comments made here are my own and are not intended to represent the official position of Alaska Air Group

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