Mode S and C detection - something changed for the better?

[RobertPBham]

Hi there,

I was just wondering if something had changed in the latest version of the software with regards to Mode S and C detection.

I was flying this weekend - and just to state the value of PAW has grown tremendously since I first bought it. The amount of gliders and planes it's flags up - whether Mode S, C or ADDB is stunning and improves every time I fly.

I digress - I did a flight this weekend from Wellesbourne, to Gloucester, Turweston, Cranfield and back to Wellesbourne. I picked up many contacts but noticed that some Mode S/C (where you only get the range circle) stated a height and that they were 'behind' - I've never seen the message 'behind'  before and thought PAW didn't know about the direction if it was Mode S or C - so I was really impressed. They definitely weren't ADSB contacts as I only had the range circle.

Is that a capability now or was it not Mode S/C?

Thanks
Rob

[exfirepro]

Rob,

We have had relative altitude for Mode C/S contacts for some time, but the use of the term 'behind' is a new one on me. Much as we would like to be able to do so, there is no way I know of that PilotAware could know the directional position of a bearingless target. It is possible that the audio reports you heard said something like 'Traffic - Alert - 500 feet - below' - this is much more likely.

Regards

Peter

[RobertPBham]

Hi Peter,

This wasn't an audio alert - it was shown on SkyDemon (I don't have the facility for audio alerts at the moment) - that's what completely threw me as I know it cannot detect in that fashion.

Once the scrub feature for track logs is implemented I'll double check - but I'm fairly positive SkyDemon reported something along the lines of '+1500 behind'. Hence the reason I was thinking wow! I definitely had the range circles and no ADSB traffic was on screen.

Thanks
Rob

[exfirepro]

Rob,

That's a new one on me - and I am currently running the latest SkyDemon Development Beta. I will keep an eye out next time I'm out.

Regards

Peter

[Ian Melville]

I had the same 'behind' alert the other day on SD. I thought there must have been a hidden ADSB contact, but could only see the warning ring for mode c/s.  Puzzled me as well.

[AlanG]

Ha ha

It must be coming up to the pantomime season and that's Tim Dawson saying "He's behind you."   

Alan
(EVFR user)

[RobertPBham]

It could be that! :-)

'Big assumption time'
I've never been that close to an ADSB target but Wellesbourne do have a ground station and when I taxi past it, I have never seen the range rings so assume that you do not get them for ADSB targets. There were a lot of gliders about on Saturday so is it possible that this was a Flarm target or similar that was being relayed via a ground station and hence had the position data? (I do not have a Flarm mouse attached).

If I remember rightly, the 'behind' message appeared after I left Turweston on the way to Cranfield.

Thanks
Rob

[RobertPBham]

Just tried playing the track through and didn't realise it doesn't appear to store Mode S/C data so cannot confirm what was happening.

[Pilot H]

How does Pilotaware and / or SD report aircraft that are transmitting both Pilotaware and Mode C ? Do you get a bearingless and a bearing resolved target for the same aircraft?

[Admin]

How does Pilotaware and / or SD report aircraft that are transmitting both Pilotaware and Mode C ? Do you get a bearingless and a bearing resolved target for the same aircraft?

These are independent of each other, there is no way to associate they are coming from the same aircraft. So if the ModeC triggers an alert due to the settings, then it will be displayed as a ring

Thx
Lee

[gilest]

Hi All

I had the same "behind" alert on SD when flying to Fishburn (have uploaded the track previously). It was very confusing and caused me to keep looking behind me! Very worryingly when I played back the track on FlightAware the aircraft was actually in front of me but never seen due to the miss reporting on SD.

Maybe someone should be reporting this to SD.

Giles

[Admin]

Hi Giles

I think Tim is aware of this, but I suggest you report on the skydemon forum

So to clarify, was this audio or visual ?

Thx
Lee

[gilest]

Hi Lee

The "behind" warning was visual on the SD app - so obviously an SD issue. Not sure where they are determining the "behind" information from when tracking a bearingless mode c/s aircraft. I will report on the SD site.

On a separate issue did you get to look at the track that I uploaded. I thought you might be interested to look at the audio warnings from PAW as they were repeated numerous times when I was following a bearingless c/s aircraft G-BYWY. Or is this expected behaviour.

Giles

[Admin]

Hi Giles

Yes I did look, unfortunately the track file does not hold all the info I require
I need to add more instrumentation to help diagnose these issues

Thx
Lee

[Ian Melville]

The behind for mode C/S targets is a Skydemon issue. I have found It can be reproduced if you are in motion, but not static.

Playback doesn't contain bearingless targets, if you are seeing them during playback, they are live targets overlaid on historic data. You need to disconnect the ADSB dongle. BTW Is it possible to have a disable USB port option on the config of the ports? I can then turn off the ADSB SDR without opening the case.