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  #1  
Old 04-05-2021, 08:45 AM
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DanH DanH is offline
 
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Default "Confirm you are not a flight of two."

I think we discussed this some time ago, but don't recall if there was an explanation.

Sometimes I contact an approach for a VFR arrival, they give me a squawk, and then come back with a request to confirm I do not have a formation partner. The scope is displaying two targets close together, when I am in fact alone.

System is a common combination, a Garmin 327 and a GDL82 ADS-B, running in anonymous mode.

Anyone know the reason?
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Last edited by DanH : 04-05-2021 at 10:23 AM.
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  #2  
Old 04-05-2021, 09:21 AM
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rv8ch rv8ch is offline
 
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Default Antenna echo?

Anything strange about your antenna placement? Reflection off those nice gear legs?
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  #3  
Old 04-05-2021, 09:27 AM
DHeal DHeal is offline
 
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On occasion I will see a "double image" of one target on my Skyview Classic screen. Sometimes the image is of my aircraft and sometimes the image is of another aircraft. It is my understanding that such images are an artifice of the ADSB system and are associated with issues within the FAA's ground network.
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  #4  
Old 04-05-2021, 09:48 AM
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Roadjunkie1 Roadjunkie1 is offline
 
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Default ADS-B dual images....etc.....

Quote:
Originally Posted by DHeal View Post
On occasion I will see a "double image" of one target on my Skyview Classic screen. It is my understanding that such images are an artifice of the ADSB system and are associated with issues within the FAA's ground network.
I will get these occasionally was well. It surprises me (although nothing should) that ATC would ask as I would think they see them often as well, likely NOT usually a flight of two. It may be something to do with the ground towers. It may be that the ADS-B broadcast is on two frequencies and they are both being picked up. An interesting quirk. One of, I think, many. My favorite is a target that suddenly shows up as a near-by problem, the Fish Finder turns red as in NEAR and it suddenly disappears! Um....what? Or the targets that are close but invisible. Another favorite...... It is a new system and things need to get ironed out......
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  #5  
Old 04-05-2021, 10:25 AM
RVDan RVDan is offline
 
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Certainly can see the possibility that the ground system isnít properly reconciling the minor difference between your ATCRBS reply, and UAT output position.
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  #6  
Old 04-05-2021, 01:14 PM
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Roadjunkie1 Roadjunkie1 is offline
 
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Default 4 engine RV-8......

Quote:
Originally Posted by RV8JD View Post

(The 747 symbol is my RV-8 ... 'delusions of grandeur', I think they call it! )
Made me laugh out loud......!!
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  #7  
Old 04-05-2021, 02:08 PM
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Thermos Thermos is offline
 
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To Dan's original question -

Target tracking software on the FAA's approach radar computers runs a "fusion" algorithm to combine individual returns from primary radar, Mode 3/S transponder and ADS-B transponder to produce (hopefully) one target for the controller. If there's common data between the Mode 3/S and ADS-B returns, like ICAO address or Mode 3 code, correlation is easy. Since you're running in UAT anonymous mode there's no discrete Mode 3 code or ICAO address to correlate between the returns. Your ADS-B position is far, far more accurate than primary radar or ATCRBS so in the absence of Mode 3/ICAO correlation, there may be some times when the fusion software isn't sufficiently sure that your ATCRBS and ADS-B are from the same aircraft, hence the target split.

Carl, there's definitely latency in the system. ATC approach radars rotate at ~12 rpm so there's the possibility of up to a 5ish second latency in Mode 3/C report changes.

HTH

Dave
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Last edited by Thermos : 04-07-2021 at 06:39 AM.
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  #8  
Old 04-05-2021, 04:23 PM
larryMar larryMar is offline
 
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I can verify what Dave is saying by experience. I now leave my ADS-B abled and have had a problem since. There is also a Garmin update that you can do to the GDL82 that is supposed to prevent "ghosting", but I have not done it.
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  #9  
Old 04-05-2021, 04:40 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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Quote:
Originally Posted by RV8JD View Post
(The 747 symbol is my RV-8 ... 'delusions of grandeur', I think they call it! )
Donít worry. Iím guessing there are a lot of 747 pilots flying passengers from point A to point B who have something that looks more like a RV on their iPads!
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  #10  
Old 04-05-2021, 06:17 PM
David Z David Z is offline
 
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Haha, I did that a few weeks ago. Albeit not in a 747, but in a work plane nonetheless. I'll call it "delusions of more fun".
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