Mixed data feeds

[Ian Melville]

I was on the ground yesterday looking at a complex PAW instalation, that the owner reported discrpencies between a PAW Classic installed with Power Flarm feed and mouse, and a standalone Rosetta. Both in range of an ATOM station.
I occasionally saw missing traffic, but the one that got me was an aircraft in the circut that kept jumping a couple of miles to the north of the circuit and back. Owner disconnected the FLARM and ADSB antenna and the jumping stopped.
Aircraft location remained correct for both units, so not a GPS issue.
Line of sight may have been obstructed at times.
I first suspected that it may be an MLAT report that is intermitantly being used, but that would not make sense as MLAT is sent to both units on the PAW frequncy. So is this an issue with FLARM direct from the aircraft in the circuit to the PF unit?
Unfortunatly I had simulator sessions to run so was not able to check the traffic table etc. Are there any logs that can help?

[Admin]

Hi Ian

2 things can help here
Firstly the track file from the unit
Secondly the icao of the aircraft allegedly jumping around
This should be enough to decode what is happening
Thx
Lee

[Ian Melville]

Thanks Lee, I will try and get that from The aircraft next weekend.

[Ian Melville]

Hi Lee, sorry it took a while to get back to you. Aircraft owner and I were never in the same space-time continuum :-)

Having got the logs and have a quick look at them, there are lots of errors on many flights. Some are minor, almost unnoticed, others just daft. If I watch the Track Replay flags, the jumps happen when there is a change in the feeds. i.e. the FLARM flag appears, or the Uplink.  I am sure this is an issue with alternate position reports. It looks as if there are gaps in the quality direct reports filled by less accurate ones, or the less accurate ones are taking precidence.

This aircraft has a PowerFlarm feed into the PAW(which may show SDSB as PF?), but I am also seeing the same on my own PAW a while back(not flown with much traffic for a while now, but can set atest this weekend)

It really saps the credability of PAW as a useful tool when you see tracks like the attached file. Hope this is an installation issue.

As for the ICAO codes of offenders, there is plenty of choice but start with
2022-08-13_10-53.trk 400E73
2022-08-19_10-00.trk 401B73

Link to files https://www.dropbox.com/sh/xsq9axlcrl7xorq/AADIic87QMRUnj1gwu0k0GS5a?dl=0

[Deker]

For info.

I have a Power Flarm Portable feeding Flarm traffic and GPS position to my PAW.
Paw also connected to iGrid.
ADSB and P3i connected to PAW

I've never seen any kind of jumping like the above in over two years of operation, I might see one jump in about 1 hrs flight at most.

Cheers,
Deker.

[Ian Melville]

Deker, do you have GPS on your PAW, or do you use the data passed through from the PF unit?

This user also has a Kandaris(sic) I think EFIS. connected. Not sure if that also has a GPS? All a bit confusing and will get more details of his setup on Saturday.

[Admin]

Hi Ian

I will download the file and take a look
But what you don’t describe, is how and where the image originates

I am guessing we are looking at two different sources of data

Thx
Lee

[Deker]

Deker, do you have GPS on your PAW, or do you use the data passed through from the PF unit?

This user also has a Kandaris(sic) I think EFIS. connected. Not sure if that also has a GPS? All a bit confusing and will get more details of his setup on Saturday.

I use the Flarm GPS antenna plugged into the Flarm unit.
The PF sends the NEMA and traffic data to PAW via the RS232.
PAW has no GPS antenna connected as data is provided by PF. (PF is set to send just Flarm and GPS. ADSB is direct into PAW using its own antenna)


Deker.

[Ian Melville]

Thanks Deker. That is the same as this installation started out. not sure that it still is and need to check

[Ian Melville]

Hi Ian

I will download the file and take a look
But what you don’t describe, is how and where the image originates

I am guessing we are looking at two different sources of data

Thx
Lee

Hi Lee. This is not the only one. I just need to swipe the time marker accross and I see more doing the same.

Note: times on Track Replay are one hour behing PAW Log.

The screen shot is from the file for the 13th between 10:11 and 10:33 (time as displayed on Tack Replay) 400E73!G

The other one I quoted above in the file for the 19th is  401B73!G-PETR between 10:13 and 10:20

in the same file between 09:59 and 10:20 (time as displayed on Tack Replay) G-OFSB, though it is possible this is a separate issue as it spends most of it time going north/south and may be an issue with the aircraft kit.

These are the obvious ones. Other aircraft jitter around.

Must dash, work calls
Cheers
Ian

[Admin]

Hi Ian

Q. was this effect seen live - or only in post processing on aircrew ?

The reason I ask, is that I took the file you provided, stripped out all aircraft EXCEPT for 400E73
and now I get this
https://aircrew.co.uk/playback/7bd5f0d4

I also looked on the groundstation viewer and saw a clean track for 400E73
https://aircrew.co.uk/playback/groundstations/?ICAO=*&RxType=*&adbVariant=*&Station=*&start=1660385400&end=1660387200

I had a suspicion about aircrew handling of the <CRLF> DOS line endings - rather than UNIX line endings
I ran the file through dos2unix, and now it all looks correct - I think I need to ask James to take a look
https://aircrew.co.uk/playback/c3072704

thx
Lee

[Ian Melville]

Hi Lee, I was alerted this time while watching it live on SkyDemon. I cannot be sure which aircraft I was watching as they were jumping all over the place, but know it was circuit bashing, so may have been G-OFSB or 4035E8!G-BUGV which is also having mild fits between 10:11 and 10:20

What you describe may have be an issue with both Aircrew Track Replay and SkyDemon?
On Saturday I will try replaying the flight from the log page into SD

I have a feeling of deja vu about this and may have raised it before from a flight of my own?
Cheer
Ian

[Ian Melville]

Spoken to John today and the only GPS is the FLARM one, which provides PAW with position reports. EFIS is not connected to the FLARM/PAW system and has its own GPS. He agrees issue is displayed on SD live.
Not much flying going on today with the fog. didn't bother to do a test.

Any further ideas?
Cheers
Ian

[Deker]

Spoken to John today and the only GPS is the FLARM one, which provides PAW with position reports. EFIS is not connected to the FLARM/PAW system and has its own GPS. He agrees issue is displayed on SD live.
Not much flying going on today with the fog. didn't bother to do a test.

Any further ideas?
Cheers
Ian

I have my PF configured to only send Flarm and NEMA data.
PF can be set to send Flarm, ADSB and NEMA, so potentially the PAW could be having to handle ADSB from two sources if the PF unit has not been configured properly.

Deker

[Ian Melville]

Thanks for that thought Deker. I don't know how John has his PF configured, but will find out. However, I would be suprised if it made any difference. I would assume that PAW can merge data streams, so it will just be two messages in quick succession.

Lee, do you have any comments?

Cheers
Ian