OGN-R Traffic Stats

[Winged_Jaguar]

I thought this might be interesting to the PAW and OGN-R community. I'm manually logging the daily traffic seen from my OGN-R station RADLEY (Abingdon, Oxfordshire) located between the Brize and Benson zones. The attached graph shows the daily variation of aircraft/gliders recorded in this area (a few days are not recorded or no traffic was observed due to poor weather). Over the period from May-Sept 2018 a total of 5,415 aircraft were observed. This was from 888 unique aircraft (many of which passed through on multiple days - they are only counted once per day even if making multiple passes) - peaking at over 200 during some afternoons. The graph is a reminder that the daily traffic can vary enormously and in some cases there can be a lot of it in a relatively small corridor (and concentrated at popular times of day). If ever we needed a reminder of why we are doing this, this may encourage our efforts on conspicuity in general and OGN-R in particular, in order to get the best possible continuous PAW coverage in the air. On several recent trips the PAW + OGN-R has helped highlight traffic ahead and been a useful addition to situational awareness and flight safety.

The biggest peaks have tended to coincide with Gliding Competitions. A useful source of possible Glider activity can be found at https://glidingtasks.co.uk/ although it can be updated quite late if the weather is marginal.
 
Chris

[Moffrestorer]

Hi WJ,

May I enquire the mechanism that you use to obtain this data? Do you have to go through the “short” or “long” listing at the foot of the 8081 diagnostic page or have you found an alternative way to obtain this data? I had thought (probably erroneously) that PAW contacts do not get listed in the short/long listings as it appears to be a record of what is received via the SDR connected to the Flarm antenna, so there will be a whole load of PAW contacts that are unrecorded flying through your patch in addition to your results. I’m not sure if there is any way to record/totalise the PAW side of OGN-R?

PS. Are you able to advise what the RND and ICA  categories refer to in your data; presumably the aircraft identifier prefix? I’m not sure myself how these differ from Flarm and OGN prefixed IDs or what it actually means!

[Winged_Jaguar]

Hi Moffrestorer,

I happened to use the long list but the short list should give the same result (from the diagnostic page :8081). I simply 'select all' in the browser and copy and paste the results into Excel, and expand out with Data and Text-to-Columns. It's crude but quick. A simple sort of the list will aggregate all lines with identifier codes in one block. As to what exactly is recorded will be for others to advise us. It appears to be just Flarm and OGN devices (not sure about PAW). I understand that some FLARM devices can be coded with the plane's ICAO number so that typically the Benson training fleet of Grobs show ICAO ID codes.

You are right that other aircraft do not appear to be recorded here. Other aircraft transiting with ADS-B, Mode C/S, military aircraft; police helicopters and others with no identifiers are all missing - however the number of these is relatively small compared to the very significant number of gliders on some days. I also run a PAW as a ground station so the traffic logs I've saved may contain the combined data of PAW + OGN-R. The format of the PAW.trk files looks messy and I haven't looked at decoding them.

The aircraft identifiers in the RTLSDR-OGN logfile are prefixed with the following 3-letter codes which I believe refer to :-

  FLR is Flarm with identities typically starting DDxxxx
  ICA is devices programmed with the ICAO identifier which can be translated to the registration (as shown on http://glidertracker.org, PAW and can be looked up on the ginfo site at  https://siteapps.caa.co.uk/g-info/ for UK regies).
  OGN Open Glider Network device
  RND Random?? The small number of contacts with these identifiers tend to appear to be in very far off and unbelievable locations so I cannot account for their origin.

Hope this helps.

Chris

[Moffrestorer]

Thanks for the explanation WJ. I confess I should have guessed the meaning of ICA, but wouldn’t have got RND! To report your ICAO code or aircraft Registration, you have to register the details with OGN. Lee encourages everyone to do this with his first “Eco-System” post on this forum, yet when looking at PAW contacts on glidertracker.org I mainly see the PAW/ ICAO Hex ID shown, not a Registration (tail no.) so I guess not a lot of people bother to register.

There’s a lot of discussion going on at the moment over on the Flyer forum whether gliders operating Flarm in “Stealth Mode” can be received by an OGN ground station. If not, as seems likely, there’s a possibility that your Traffic figures could be even higher if this Mode were being used by some participants during  those gliding competitions! Also, as you point out, I don’t think PAW contacts are included in your data. The OGN station does not detect Mode S at present, and certainly doesn’t detect ADS-B or Mode C returns. Very interesting graph all the same!

Regards,

Chris

[PaulRuskin]

I'll copy what I've just posted over on Flyer, having been alerted to it here!

Stealth mode / No track etc were entirely rational features for Flarm and OGN to introduce, and led to a more rapid take up of both systems - which is a good thing.

Stealth mode meant that competitive glider pilots (and gliding is a competitive sport at times, remember) could use Flarm without worrying about the competitive impact. In fact, the benefits of not using stealth mode (such as spectators being able to see what's happening in competitions, and take off and landing logging) mean that it's very rarely used. So, basically, don't worry about it.

No-track was introduced by Flarm and OGN after OGN started, because there were some serious privacy issues - particularly in Germany where people are more sensitive about that sort of thing than in the UK. The feature made the problem go away, but again, I don't think it's used very much.

AIUI in any case, OGNR will rebroadcast stealth mode gliders. Perhaps not no-track ones, whose packets probably get dropped in the OGN receiver.

As to 7000 Flarms in the UK - I don't believe it. It's possible that 7000 have been sold to the UK over the history of the product, I suppose (though the propensity of glider pilots not to throw stuff away makes this unlikely in my view). But, there are (o) 2000-2500 gliders in the UK (2310 according to wikipedia), and as other people have pointed out, the penetration of Flarm into other sectors in the UK is low. Anyone who keeps an eye on the OGN plots knows this. I'd have thought 2000-2500 active Flarms is much closer to the truth. [so same order of magnitude as PAW, and currently a lot more than ADSB in GA aircraft].

Paul

[Winged_Jaguar]

Is it possible that the those marked as RND are the cloaked ones? The identities are possibly real but the associated location data appears to be randomised which might account for the bizarre reported Long/Lat positions which can be thousands of miles away. I've only logged 22 unique RND identities so far. However if this is the case one might argue going forward that in terms of privacy v safety that it is the identity which ought to be hidden not the location. 

Chris

[PaulRuskin]

>Is it possible that the those marked as RND are the cloaked ones? The identities are possibly real but the associated location data appears to be randomised which might account for the bizarre reported Long/Lat positions which can be thousands of miles away. I've only logged 22 unique RND identities so far. However if this is the case one might argue going forward that in terms of privacy v safety that it is the identity which ought to be hidden not the location. 

No, don't think so.  AIUI the location is transmitted accurately.  Any dithering is done in the Flarm receiver, based on the flag set.  Flarm does have the ability to randomise the ID.  The occasional sight of ranges of 5000km+ is an error somewhere else - probably in the web page part of the OGNR receiver, since even when that happens, the correct locations of the targets appear to being sent to the APRS servers.

What happens in the OGN web pages (live.glidernet.org etc) is different and based on settings in the OGN DB - for example the Flarm ID will not be shown on some sites if an entry is not made in the OGN DB, and it's also possible to register but not show ID, or not be shown at all.

Paul

[Admin]

The occasional sight of ranges of 5000km+ is an error somewhere else - probably in the web page part of the OGNR receiver, since even when that happens, the correct locations of the targets appear to being sent to the APRS servers.

Just to clarify this, what is happening here is that when the OGN-R powers up it 'thinks' it is located at lat=0/lon=0
So any received traffic appear approx 5000km away

The OGN-R client is listening to the OGN client talk to the APRS servers.
At some point the OGN client will tell the APRS server 'I am here' providing the lat/lon correct numbers
This is 'passively snooped' by OGN-R which now says, OK, we are at lat=X/lon=Y
At this point the numbers in the web page 8082 are corrected

Bear in mind, that until this point - no traffic is relayed, or sent to the APRS servers from the PilotAware side of the installation

Thx
Lee

[Winged_Jaguar]

Thanks Lee,

That makes sense however this does suggest that the connection may periodically reset back to location 'unknown' as my OGN-R unit confirms that it has been up for several days and the most recent RND record was received today.

  APRS.Server[0] -> aprs.glidernet.org:14580
  connected to 88.99.111.134:14580
  connected for 111h12
  KiloBytes sent/received 7986/1521

RND919DBF [    1/    1sec]   C:0:919DBF  <249.0m/s> < 5.0dB>, <11.0bit/packet>, < -3.08(0.00)kHz>
153728: [ +48.64621,  -4.18685]deg    0m +178.4m/s 249.0m/s 235.6deg -44.8deg/sec 2 23x02m 00f_ -3.08kHz  5.0/11.0dB/2 11e  397.2km 312.2deg  -3.5deg   ?   ! 

Chris