TIS traffic glitch?

[hoyden]

Yesterday while flying NW of MSP I was scanning outside and when I look inside Skyview was displaying traffic right on top of me with 0 altitude and a direction pointing to about the 1:30 position. A momentary panic and furtive look outside again.

There was nothing outside and a few seconds later the traffic disappeared. I am guessing the TIS glitched and processed me as traffic on top of myself.

 

[trevpond]

Hi,

Are you using a ZAON XRX? I use one and get ghost aircraft showing up a lot, figured that they are my aircraft.

Trev ;D ;D

 

[mmarien]

It would be a glitch for TIS but pretty common for a ZAON as Trev noted. My ghosts are usually below me. I just assumed they were reflections of my own xponder off something shiny down there. Because it happens often I didn't think the ZAON worked all that well but it has picked out aircraft before I do lots of times. A couple of days ago I watched a 737 on final cross my screen while I was on a base. I knew he was there. It was just a surprise to see a big yellow target on the screen. Don't see them that threatening often ;D

 

[brianreid]

I have the full Dynon ADS-B and the same thing happened. I was flying between Cleveland and Akron and TWO targets would show up at the same position and altitude. After intensive scanning and some evasive maneuvers (just in case) they just disappeared. They showed up and disappeared several times. I finally decided the Cleveland and Akron radars were each showing me as a target and the ADS software didn't (or couldn't) filter me out properly.

 

[hoyden]

My glitch was with the Dynon transponder, no ADS-B. I've been flying the Skyview for about 2 years and this is the first time I've seen a glitch.

 

[Garrett]

It is due to a glitch that is in the FAA's TIS system and has been has been their since it's inception well over a decade ago. The aircraft will sometimes see it's own shadow no matter who's equipment is onboard.

 

[Dynon]

So two things are going on here:

On the TIS, side, I believe Garrett's right about that. TIS basically knows about your aircraft and says "here are all of the threats that you need to know about right now". It basically does all of the screening for you and only tells you about aircraft that are near you.

On the ADS-B side, the system doesn't screen traffic in exactly the same way, but it does include information that lets systems like SkyView filter out your own traffic target. From what we've seen, sometimes the ADS-B system doesn't correctly tag your aircraft in the way it should. We're keeping an eye on this (and we've seen it ourselves when flying).

The implementation challenge of trying to do anything too clever is that when there's an actual threat nearby, even when it seemingly pops out of nowhere, you want to know about it. Inventing the right screening mechanism that ignores phantom own-ships while including every actual threat is of course very possible, but it's easy to get it very wrong too.