Foreflight/Stratus ghosts?

[Let'sgoflying!]

As I was approaching a field yesterday, FF was displaying an aircraft that was just behind me and 1300' above me.
I did some turns to look and saw nothing. It seemed to follow me.
I did another turn, this one 90°, to see if I could shake him and kept announcing on the radio. 'He' stayed with me and no radio calls. I descended & accelerated, and he descended & kept up with me. Sometimes he was 1/2mi behind me, or ahead of me, and beside me, or right on me. I could see one other a/c, an airline probably 20mi away in the 30's.
The target disappeared and I was sure there was nothing there after scanning & turning so I proceeded to land. Only other traffic seen and heard was a guy departing.
This was in the mountains, 1000' from terrain at times.
What'd I do wrong?

 

[SCCutler]

Nothing, it's a symptom of the tech. You were picking up you.

 

[Let'sgoflying!]

Figured; thanks.
The tag had no ID to it unlike the other traffic I've seen eg "N1234"
Did I imagine it, or did the ghost change color as it 'got closer'? Might have been the morning light changing through the airplane during turns. Is there an audio alert for traffic?
I presume it only shows targets having ads-b out. Ie <1% of the GA fleet?

 

[John Collins]

Ghosts occur when your GPS position and altitude as understood by your onboard equipment differs from your position and pressure altitude detected by radar. ForeFlight uses a filtering scheme that involves repeated matches in the position and altitude of a target. It does a much better job when you have ADSB Out installed beecause it can then use the own ship GPS altitude to compare with the Stratus altitude, instead of target pressure altitude verses Stratus altitude. I have both Stratus and certified GDL88 system. Even the GDL88 will occasionally see ghosts.

 

[Let'sgoflying!]

a couple of more recent examples.

 

[Let'sgoflying!]

wont allow >1 photo per post?

 

[SCCutler]

a couple of more recent examples.

That is one FAST Bellanca!

 

[Let'sgoflying!]

thankfully fast enough to outrun the Marfa Ghost!

 

[Bill Watson]

I had a similar thing happen to me over eastern PA. I've on occassion seen my shadow usually within a mile or so of my position. It's obviously an echo of some kind.

In my case over easter PA a target started some distance from me on a converging flight path at a slightly lower altitude. I was on an IFR clearance only 100s of feet above an undercast. I watched this target for some time before getting concerned as it closed in.

However, a check with ATC indicated no iFR traffic or radar returns. The undercast should have made a real aircraft easily visible.

With head on a swivel I watched the target merge with mine. Very spooky.

On the other hand, yesterday on a CAVU day with 75 knot winds I watched a target circling at 10K plus/minus 200' as I cruised by at 9K. ATC could see the target but wasn't talking to it. It was turned away from me at my 9:00 but then it came around and the 75knot wind had him closing on me at a high rate of speed. I struggled to get an eye ball on the target but finally did despite being at my 7:00 and head on. He closed to within little more than a thousand feet - his lateral distance being no more than the altitude difference.

One thousand feet is fine for passing aircraft in many situations but this turned out to be Cirrus doing lazy ovals at 10K between Hickory and Statesville NC. He never saw me and wasn't talking to anyone though for a second I thought he was trying to fly formation with me. I watched him make 1.5 more turns before he fell off my map.

What the hell? It was all perfectly legal though I would say ill advised. I saw him only because of ADSB and he never saw me I'm sure. it's an area that I know from experience is often filled with Charlotte airliners at 9 - 12k as they enter the Class B, but on this day I'm sure they were departing to the north. Doing lazy circles at an IFR altitude within 10 miles of a Class B is, well, for glider guiders only.

Someone recently said something to the effect of "screw ADSB, I'll depend on my Mark 20 eyeballs". I say "but for the grace of a big sky, I want every tool available to me to help me keep it in one piece". Whew!