Range spikes on VRS World

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mezoo
Posts: 23
Joined: Sat Jan 04, 2014 6:32 pm

Range spikes on VRS World

Post by mezoo » Wed Jan 21, 2015 9:07 pm

When looking at the range of my receivers (and others) on de.vrs-world.com there are strange long range spikes toward regions in which I dont have any long range reception.
These long range spikes do not appear on my local screen.
Sometimes I also noticed that aircraft are being assigned (for a short time) to a receiver which is far away (> 500km) from the position shown.
(This probably causes the spikes)

Could this be from the server somehow losing track of the correct receiver ?
e.g. from data glitches during data transmission.

I have the impression that the spikes seem to occur in directions were there is an overlap between different receivers.
mezoo

agw
Posts: 2241
Joined: Fri Feb 17, 2012 3:20 am

Re: Range spikes on VRS World

Post by agw » Thu Jan 22, 2015 12:32 am

There are some aircraft that routinely send garbage positions - there's a Bluebird 737 that does that. The trouble is that it sends them for long enough that they get accepted as valid. Looking at how to address those is on the list, I just haven't gotten around to it yet :)

mezoo
Posts: 23
Joined: Sat Jan 04, 2014 6:32 pm

Re: Range spikes on VRS World

Post by mezoo » Thu Jan 22, 2015 8:39 pm

I have seen some of those spurious aircraft.

But what I am referring are spikes which only shown up on the map from the VRS World server but not on my local one ?
If it was an aircraft shouldn't the spikes appear on both maps ?

That's why I thought it is an issue with the data amalgamation on the server or data transfer problems.

Mezoo

agw
Posts: 2241
Joined: Fri Feb 17, 2012 3:20 am

Re: Range spikes on VRS World

Post by agw » Tue Jan 27, 2015 12:36 am

Ah OK - so are you saying that you're looking at your receiver on VRS World and your local receiver on your local site, and the spikes appear on the remote plot but not your local plot? If so then my guess would be that VRS World might have changed the raw decoding settings to pick up more aircraft at extreme range - that could cause more erroneous messages to be taken as valid. I've got a vague notion that they might have changed the raw decoding settings.

But yes, all things being equal you would expect the remote and local plots of the same receiver to be roughly the same, assuming that both sides are seeing the same messages. I suppose there is a timing issue with messages going over the rebroadcast server, if they end up sitting in the buffer then two messages that were picked up by the receiver say 50ms apart could end up being received by the remote side 1ms apart - likewise if there was some delay in sending the second of the two they might arrive 100ms apart. That would cock up the speed checks and might cause invalid messages to be accepted as valid.

In both cases that should be fixed as a side-effect of the upcoming (when I get time to do it) Flight Aware rebroadcast format, assuming that VRS World switch over to that when it becomes available. With that format the remote side doesn't do any raw decoding.

mezoo
Posts: 23
Joined: Sat Jan 04, 2014 6:32 pm

Re: Range spikes on VRS World

Post by mezoo » Tue Jan 27, 2015 7:07 pm

Yes, thats what I mean.
My receiver viewed on my local server does not shown spikes.
But my receiver (and others) on VRS World show spikes.

I'll wait and see what happens in future versions.

Thank you for all your efforts !!

Mezoo

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