PAW track log understanding

[Deker]

Hi SGS66,

The U represents data Uplinked from a OGN-R ground station.
U M indicates that this was an MLAT(ed) aircraft
(U G would indicate a Flarm aircraft)

Due to the way in which a MLAT position is calculated from triangulation from various base stations, this can cause the track to appear not smooth.

This is not actually a problem of the Aircrew playback, but a function of the MLAT position calculation.
Deker.

Using Aircrew analyser and PAW with the latest software.
I could ask a number of questions but here is the first one.
 
Considering my flight into Lee on Solent yesterday I note using Aircrew an aircraft well ahead of me to land with P U M codes, ie no C no S codes - how does U and M come about (SkyDemon also displayed it whilst I was flying but I did not bother to look closely at the Ipad as the Pilot of the said aircraft was giving good and timely position reports). Presumably it's a problem with Aircrew ? It certainly looked like U data being used as the profile was not smooth like an aircraft with a P designation.

[SGS66]

Deker,
Let me put the question another way - why is a paw
aircraft being reported to me as U M with a jerky profile ?
Phil

[Admin]

Hi sgs66
I presume you read and understood the mode-s/3d document before enabling the feature ?
So this is based upon mlat, much more accurate than bearing less
Not quite as accurate as gps, hence some of the calculation errors
Thx
Lee

[neilmurg]

Hi SGS66,
The U represents data Uplinked from a OGN-R ground station.
U M indicates that this was an MLAT(ed) aircraft
(U G would indicate a Flarm aircraft)

SGS66 said that aircrew showed the target as PUM, implying it was a Pilotaware emitter.
As I understand it the aircraft is an MLAT'd target, not a PAw aircraft. SGS also knows this, he already indicated that the targets track implies MLAT. He's asking about the contradictory indication.

I don't know if Skydemon would show it as Pilotaware and MLAT, or what PAw radar would show

[Paul_Sengupta]

Did it show P from the beginning? It might have been uplinked MLAT to start with then, as a PAW user, came into direct range?

Or does anything uplinked show P anyway as it's being received through the bridge?

[Ian Melville]

I had an odd one but on a similar vein a few days ago.

Aircraft approached me and was shown as derived from MLAT, but then became a red ring. Alternate text on SD still showed it as MLAT. Spotted a second one later on.

Short Video of GBPAY
https://www.dropbox.com/sh/hrf0moj1snditu5/AADnGCGqfJaDoRwG2UxFd9Y5a?dl=0
Folder contains screenshots and log file as well Lee. The earlier track file shows GSKKY which is the one that first alerted me to this.

[Admin]

The flags are ‘sticky’, which means they latch
So in Ians case what was showing was an aircraft which historically had received mlat
This was no longer valid, but direct bearingless was valid
If you look at the traffic screen, and there is no figure for distance
Then it is bearingless

Not sure if it is clear. But P is set from a rebroadcast as well
So PUM, mlat uplinked via Pilotaware

Thx
Lee

[Ian Melville]

Any particular reason why they are ‘sticky’?

[neilmurg]

Can I guess?
If message sentences are incomplete, after several repeats the full sentence will become fully populated

[SGS66]

Lee,

Can I suggest in the combined code P U M, the code U is redundant and the P is misleading. M says it all, this data must be uplinked to our PAW equipment from a ground station, so M is enough.

Then you could use the P code when it is a true P-P interaction.

What is more M also implies A,C,S so code M speaks volumes.

Phil