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Author Topic: Live reception/network reception - what happens at the join?  (Read 26317 times)

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Fenris

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Live reception/network reception - what happens at the join?
« on: December 30, 2008, 12:17:20 AM »
As I have not yet purchased a Radarbox, I have a question about the effects seen where live aircraft reception and 5 minute delayed reception meet.

Imagine the case where an aircraft is approaching you, but is still below the radio horizon so that you receive it's transponder via a server-delivered network connection. As the aircraft continues and comes above the radio horizon, suddenly its signal reaches detection threshold and it becomes a live reception signal. Does it suddenly jump forwards on its track, as positional reality is suddenly applied? And does a similar effect occur in reverse? Where a live aircraft goes out of range and appears as a network-supplied track, and hence suddenly seems to regress 5 minutes into the past and its position now appears in the area covered by live reception despite it already having travelled the same track for real 5 minutes ago?

I'm not totally convinced by this 5 minute delay for network traffic, I'd rather like to understand the rationale behind it. I know it's claimed to be for security reasons, but I can see that if someone has a Radarbox within live range of an airport then that argument can't apply and surely people with ill intentions are more dangerous at short range than they can be at much longer ranges?

AirNav Support

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Re: Live reception/network reception - what happens at the join?
« Reply #1 on: December 30, 2008, 12:57:59 AM »
The network works well and the delay also works as explained:

Aircraft from local to network:

Aircraft is picked up locally and then you loose reception with it. The software remembers that you have picked up this aircraft and its not displayed on the network for you untill it passes the point you last lost reception (uses timestamps and other programing means) . In theory you can track the aircraft just after it left your reception 5 minutes later.

Aircraft from network to local:

Aircraft is shown on the network as its not been picked up locally yet. As soon as its picked up locally that local data is more important and it shows the local data. In theory as the network data is 5 minutes delayed there is a jump.

We won't go into why the delay is there as that topic has been discussed endsley and a quick search of the forum will bring results on that for you.
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Deadcalm

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Re: Live reception/network reception - what happens at the join?
« Reply #2 on: December 30, 2008, 09:02:41 AM »
I have to say that I've NEVER experienced a mere 5 minutes in the transition, it's usually 20 minutes to half an hour.  I've made a point of watching the progress of specific aircraft between France and adjoining countries (where there appears to be ample network coverage) in both directions, and targets just disappear for ages.  That's one reason why I've been keen on reasonably accurate locations of active network members at any particular time, to assist in the rationale of why many targets are "invisible" for so long.

I don't doubt, though, that other users aren't necessarily experiencing these long disappearances.  It's probably a combination of flight level, and the location of other contributors that have a direct effect on my experiences.

I'd be interested to know what others have found.

DC
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tarbat

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Re: Live reception/network reception - what happens at the join?
« Reply #3 on: December 30, 2008, 09:48:27 AM »
One question I have about network aircraft is about timeouts.  For example, the network aircraft pictured below stayed on my map for about 10 minutes, always at the same altitude and speed.  It wasn't moving.  Now, my timeouts are:
MyFlights - 20 / 80 seconds
Network - 35 / 65 seconds

So, why didn't the aircraft timeout?  Or do the timeout settings for the user who is actually receiving the aircraft also have an effect?  So, if the user who was receiving this aircraft had very high local timeouts, would the aircraft still appear on the network many minutes after the user had lost reception?

Allocator

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Re: Live reception/network reception - what happens at the join?
« Reply #4 on: December 30, 2008, 09:56:42 AM »
DC,

If you are loosing aircraft for 30 minutes, at an average 450 mph, then you are talking about loosing aircraft for 225 miles - surely this isn't what you mean?

I have both live and Network traffic going through my overhead all day long, as I'm about 30 miles south of WAL on a very busy route.  I can't say that I honestly even notice the transition between Network/live/Network, although when I was involved in beta testing in the very early days, I did suggest a "tweak" in the priorities to make sure that live traffic always had a higher preference when it came to displaying aircraft.  This was done and improved matters a great deal.

Fenris,

Like you, I had serious doubts about the 5 minute delay in Network traffic when I heard about it first.  I bought an SBS-1 over two and a half years ago on the promise of the MapModeS Kinetic network that promised all live data - this was never released and will never be released due to legal and technical problems.  With regard to the RadarBox Network delay, I argued that the RadarBox live traffic should be delayed by 5 minutes too so that all traffic showed in the correct position relative to each other.  Fortunately, AirNav didn't listen to me and stuck to the live live traffic and the 5 minute delayed Network traffic.

Generally, when you are watching Network traffic, it's going to be far enough away for the delay to be insignificant.  With live coverage going out to at least 150 miles and often 200 to 250 miles, then anything inside this at a reasonable height is going to be plotted as live anyway.

The "5 minute delay" is all that's keeping "big brother" off our backs at the moment, as it's an (unwritten?) internationally accepted security requirement.  About 2 years ago, one of the UK tabloid newspapers did a double page scare story showing the SBS-1, a terrorist with an RPG and a nice picture of an airliner.  Fortunately, nothing came of this, but in the current climate of fear, it wouldn't take much for us all loose the enjoyment we're having following aircraft by Mode S.  Whatever you do, don't try to apply logic to the 5 minute delay argument :-(


Blackthorn

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Re: Live reception/network reception - what happens at the join?
« Reply #5 on: December 30, 2008, 09:57:41 AM »
Hi DC

I have been checking this out and have found it is 5 mins but if the aircraft is switching between local and network I need to disable local flights otherwise it does not show up on Network 5 mins later.

I hope this makes sense?

tarbat

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Re: Live reception/network reception - what happens at the join?
« Reply #6 on: December 30, 2008, 09:59:25 AM »
Blackthorn, out of interest, what are your timeout settings?

Blackthorn

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Re: Live reception/network reception - what happens at the join?
« Reply #7 on: December 30, 2008, 10:04:08 AM »
Hi Tarbat

60 secs

tarbat

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Re: Live reception/network reception - what happens at the join?
« Reply #8 on: December 30, 2008, 10:07:43 AM »
Blackthorn, is that:
MyFlights - 60 / 60 seconds
Network - 60 / 60 seconds

I'm trying to establish what effect (if any) timeout settings have on transitions from/to network/local.
« Last Edit: December 30, 2008, 10:11:03 AM by tarbat »

Bill

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Re: Live reception/network reception - what happens at the join?
« Reply #9 on: December 30, 2008, 10:13:05 AM »
Tarbat - as the other person in NE Scotland (!) I have the suspicion that your aircraft is one of mine.  I also suspect that you are correct in your assumption about timeout times.  Myflights is 300 / 1440 and Network is 120 / 1200 to, er, mmh, attempt to emulate the long trail lines available on the alternative system -which I rather like (and incidentally something I requested as an upgrade many revisions ago).

Allocator

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Re: Live reception/network reception - what happens at the join?
« Reply #10 on: December 30, 2008, 10:16:10 AM »
OK, here's a transition from the Network to Live - about a 10 mile "jump"? Note the times on the screen shots.

I'm using:
30 and 60 Live
90 and 180 Network

The subject aircraft is EZY38CR in the Isle of Man region.  Click the links below the pictures for full size.



http://farm4.static.flickr.com/3094/3149567095_612676c391_o.jpg



http://farm4.static.flickr.com/3127/3150407136_363cc5108b_o.jpg



http://farm4.static.flickr.com/3100/3149580445_da2d8389c2_o.jpg
« Last Edit: December 30, 2008, 10:18:02 AM by Allocator »

tarbat

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Re: Live reception/network reception - what happens at the join?
« Reply #11 on: December 30, 2008, 10:16:29 AM »
Thanks Bill.  I suspect that your 300s + 1440s (total of 1740s) on local explains why the aircraft stayed static on my map.

Airnav, surely this is a bug.  Just because the local user chooses to have a long timeout on their local traffic, that shouldn't mean that I also have that long timout when I receive the aircraft on the network.  Surely my own Network Timeout settings should take precedent.

Could this also explain some of the other anomolies being reported in this thread?
« Last Edit: December 30, 2008, 10:23:32 AM by tarbat »

Blackthorn

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Re: Live reception/network reception - what happens at the join?
« Reply #12 on: December 30, 2008, 10:17:35 AM »
Blackthorn, is that:
MyFlights - 60 / 60 seconds
Network - 60 / 60 seconds

I'm trying to establish what effect (if any) timeout settings have on transitions from/to network/local.

Myflights 60/60
Network 90/180

tarbat

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Re: Live reception/network reception - what happens at the join?
« Reply #13 on: December 30, 2008, 10:19:05 AM »
Thanks Blackthorn.  I think that rules out timeouts as the cause of the problem you're seeing.

Although I can't say I've ever had to disable local flights when an aircraft transitions from local to network.  And I see a lot of aircraft that go from local to network.
« Last Edit: December 30, 2008, 10:20:48 AM by tarbat »

Blackthorn

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Re: Live reception/network reception - what happens at the join?
« Reply #14 on: December 30, 2008, 10:26:01 AM »
Thanks Blackthorn.  I think that rules out timeouts as the cause of the problem you're seeing.

Although I can't say I've ever had to disable local flights when an aircraft transitions from local to network.  And I see a lot of aircraft that go from local to network.

I have just tracked flight COA46 Houston-Schipol and I had to switch off local for it to reappear on Network.