360radar network

[tnowak]

General question: Is the 360radar.co.uk ground receiver network capable of receiving PAW transmissions from aircarft?
If so, does the PAW data enhance MLAT processing by 360radar?

Thanks

Tony

[exfirepro]

Hi Tony,

I hope Lee doesn’t mind me posting on behalf of the Team. I know he and the others are extremely busy at the moment trying to get the new software and documentation released.

I’m not an ‘expert’ on 360Radar, though as a ‘Contributor’ through my OGN-R Ground Stations and through my involvement in PilotAware Mode-S/3D Development and Testing, I probably have a better than average awareness of how Phil’s system works.

The short answer to your question is that Phil will have access to P3i data via the OGN-R station network, but he will not have ‘direct’ reception through the rest of the ‘360Radar’ Network as by far the majority of 360Radar receivers will be 1090MHz only.

I presume your concerns are raised because of the blatant and disgraceful attempt on the Flyer Forum to undermine the rollout of PilotAware Mode-S/3D by trying to discredit the quality of 360Radar’s data. Rest assured that we are all far more interested in working to ensure system reliability and robustness than engaging in what would inevitably become yet another ADSB v PAW slanging match on the Flyer Forum. The results of our long-term Mode-S/3D testing (which will prove the quality of the data) will be released at the appropriate time chosen by the Team, not as a knee-jerk reaction to ‘Cub’s’ obvious trolling attempt.

Best Regards

Peter

Regards

Peter

[PaulSS]

Hi Tony,

I'm sure I'll be corrected if I'm wrong but 360Radar receives Flarm and ADSB and uses Mode S for multilateration. They do not mention PAW reception, nor data through the OGN-R network.

It does seem a shame, though, that since PAW knows where it is (same as ADSB) and 360Radar signals come from OGN-R stations to the aircraft, that PAW doesn't go the other way and send position data from the aircraft to 360Radar via the OGN-R stations. It would save them having to multi-laterate (is that a real verb) if the aircraft had PAW and Mode S but no ADSB Out.

[Pidea]

Thanks to Lee for pointing me at this.  I'm Phil, the guy behind 360Radar.

360Radar consists of a network of approximately 900 Raspberry Pi-based receivers and around 40 Windows-based ones scattered across the UK from the Outer Hebredies, Orkneys to Lands End all the way to Dover.

Each of these runs our multilateration client and they collaborate together to calculate in realtime the position of Mode S aircraft (those ones that don't transmit their locations).  In order to successfully MLAT an aircraft we need a minimum of four receivers to see the aircraft at the same time.  Despite this challenge we can MLAT down to less 1,000 ft in some parts of the country but this depends on the terrain and the number of receivers (and we're always looking for more locations to site a receiver especially if you're in a remote location).

An increasing number of the PilotAware groundstations also run our MLAT-Client (they need a second SDR fitting) which helps to improve our coverage as many of these are on airfields and these tend not to have too many obstructions around them.  As a result these provide some excellent coverage.

Some of our receivers also upload ADSB messages from aircraft that do transmit their locations.  We don't need as many of these as only one receiver is needed to locate these aircraft.

We also get a feed from the OGN network which allows us to track PilotAware equipped aircraft, gliders and any other FLARM equipped aircraft such as the RAF Grob Tutors and Tucanos.  No 360Radar receivers (unless a PilotAware one) receive PilotAware data as they would require a second SDR and aerial.

So what happens to all this data ?  A subset (traffic below 10,000 ft) of this is then sent to PilotAware for rebroadcast by PilotAware groundstations whilst the full feed is sent to 360Radar and merged with all the other data for our contributors and subscribers to view.

But what about those aircraft that are only Mode A or Mode C ... well, we're working on tracking those too ;-)

[Admin]

But what about those aircraft that are only Mode A or Mode C ... well, we're working on tracking those too ;-)

Phil you have now given the game away 

There have been a number of questions about accuracy of the data, let me explain how we are measuring the position reports (a fuller description is in preparation)

We have measured from 2 viewpoints, in-aircraft and ground-station

For the participants of the trial, they have been submitting their in-flight data recorder data back to us for analysis.
If the aircraft is Mode-S equipped, this is perfect, because this allows us to measure the round trip delay and accuracy of the on-board Mode-S, captured by 360Radar, sent to the central server, relayed to the OGN-R, and uplinked to your PilotAware. At this point of Mode-S reception we can measure the reported position of our MLAT (self) to our current GPS reported position. We now have an absolute error value for a reported MLAT sample.
We gather 1000's of these and can produce cumulative and statistical data.

At the ground station, we can do something similar, but this does not require the aircraft to be running the trial software. So for any aircraft equipped with PilotAware and a Mode-S we can do the same thing, we get a position report from the PilotAware in flight, or we get a position report via the relayed MLAT position of the same aircraft. At this point we can look at the time difference between the two reported positions, and the absolute difference in position form both GPS data reports.

We have been capturing this data in the air from the trial participants since the start of the trial, and from the ground stations, for the last couple of weeks - so you can imagine we have a lot of data !


Thx
Lee

[mariko]

But what about those aircraft that are only Mode A or Mode C ... well, we're working on tracking those too ;-)

How!?!? Is it Really possibile with a omnidirectional aerial?

[Pidea]

How!?!? Is it Really possibile with a omnidirectional aerial?

Yes, very early tests suggest that it would be possible in time for some aircraft as long as they use unique squawk codes.

[mariko]

How!?!? Is it Really possibile with a omnidirectional aerial?

Yes, very early tests suggest that it would be possible in time for some aircraft as long as they use unique squawk codes.

really interesting! The tests consist to assign a C answer to an unique A answer with the same signal strenght, and use MLAT to determine horizontal position (as for S trasponder)?

[Pidea]

really interesting! The tests consist to assign a C answer to an unique A answer with the same signal strenght, and use MLAT to determine horizontal position (as for S trasponder)?

Nice idea but unfortunately there's no easy way to get the signal strength from the receiver for a Mode A/C reply

[mariko]

really interesting! The tests consist to assign a C answer to an unique A answer with the same signal strenght, and use MLAT to determine horizontal position (as for S trasponder)?

Nice idea but unfortunately there's no easy way to get the signal strength from the receiver for a Mode A/C reply

Understood. So you can multilatering the horizontal position of an A unique squawk code, but without vertical position. Or you have a different way to combine A answers with C answer... I'm getting curious... 

[Pidea]

Understood. So you can multilatering the horizontal position of an A unique squawk code, but without vertical position. Or you have a different way to combine A answers with C answer... I'm getting curious... 

You'll have to stay curious I'm afraid 

[Cub]

I presume your concerns are raised because of the blatant and disgraceful attempt on the Flyer Forum to undermine the rollout of PilotAware Mode-S/3D by trying to discredit the quality of 360Radar’s data. Rest assured that we are all far more interested in working to ensure system reliability and robustness than engaging in what would inevitably become yet another ADSB v PAW slanging match on the Flyer Forum. The results of our long-term Mode-S/3D testing (which will prove the quality of the data) will be released at the appropriate time chosen by the Team, not as a knee-jerk reaction to ‘Cub’s’ obvious trolling attempt.

Peter

I am sorry that you regard my 'blatant' attempt to understand the integrity of the position information supplied by 360Radar to the latest iteration of PAW as 'disgraceful' and 'trolling'.  It is neither.  I have worked tirelessly for the last 10 years in a variety of roles to improve safety in GA and have worked particularly closely with Tim Dawson at SkyDemon in his delivery of SkyDemon Traffic to enable robust and reliable proximity alerting.  If, as you suggest, you are able to prove or quantify the quality of the data presented to SkyDemon and other applications processing PAW data than I will be the first to celebrate this additional alerting capability available to the GA fleet. 

I believe my challenge as to the potential problems in generating proximity alerts from anything other than emphatic position information is reasonable and I resent any suggestion that I am in any way trolling when my concerns are based around a genuine HMI safety concern, which incidentally will form a percentage of my day job in a few weeks time.

I feel as a PAW and 360Radar customer that I don't deserve to be referred to in on the User Forum in derogatory terms and certainly not when my concerns have not been addressed via polite challenge elsewhere.

It would be far nicer if we could play nicely and constructively to achieve our mutual aim.

Cub

[Ian Melville]

Sorry Cub, I have to agree with Peter. I saw your post and chose not to respond.

You have Lees contact details yet you chose to post a public question to Lee.

IIRC you also offered to assist with verifying the accuracy of tracks, have you done this?

This comment you made, make me think WTF.

I question whether the obvious inaccuracies in the track are good enough to generate accurate traffic alerts using something like SkyDemon Traffic?

That would imply that you (and from later posting Tim Dawson and Gaznav) think that MLAT should not be permitted as it cannot match your radar trace?. I know I would prefer an MLAT  report, to what is currently available, just altitude and no clue as to direction or range. Presumably, you also objected to the Zeon PCAS XRX on the same grounds?

Yes I know we could all have ADSB out, but we don't yet, and the majority won't any time soon. I want to be safe as possible today, not hope that it may all work sometime in the future.

[Cub]

A couple of points;  I don’t have Lee’s contact details and I have never knowingly met him although I do think I may have had a teleconference involving him, some years ago. I have met Keith Vinning on a number of occasions both professionally and personally but have never managed to get a straight answer about this topic or several other issues despite his clear immense enthusiasm for the functionality.

I don’t feel MLAT should not be deployed at all. I am a huge fan off MLAT generally and have been consistently impressed with what NATS ‘Crystal’ network achieves utilising the technology.  As far as 360radar is concerned, I am full of admiration for what has been achieved not least because I am a very early adopter of SBS1 and 3 receivers and Planeplotter enthusiast. However, my enthusiasm is tempered by my other passion which is GA safety and the robust and safe deployment of this sort of functionality in the GA fleet.

The PAW team can, of course, do whatever they want but I have got a particular interest in how PAW data and other aircraft positional data is processed and presented in third party apps. I have a lot of experience in HMI design in relation to ATC tools and functionality and latterly have worked quite closely with that amazing talent, Tim Dawson in the concept of operations and design of SkyDemon Traffic.  My concern was and remains that without a high degree of positional accuracy or at least a measure of likely accuracy in relation to each target that the subsequent processing and alerting in relation to those targets can be misleading and at worst, dangerously disorientating.

All I (and I suspect SkyDemon) are trying to establish is how, ahead of the PAW multilaterated data going live, those multilaterated targets will be differentiated from those targets with an emphatic position source and what accuracy is going to be associated with the multilaterated ones. Once that is known, clever people doing clever things with PAW’s clever data can ensure safe and robust presentation of that data.

No more, no less and certainly not worthy of some of the vitriol directed at me by some of the team developing a product I have purchased as a customer.

[neilmurg]

Publish the software upgrade
Then we'll be talking about what PAw with Mode S + multilat is showing vs scare stories

Why would you not welcome an improvement in EC?
Only if you thought it was so good it damaged the case for enforced ADS-B