FlightAware Discussions

Understanding the correlation between aircraft and messages

Since following the advice on upgrades, my station is doing well.

Please would somebody help with the correlation between aircraft seen and messages received?

In my local area, I have 487 flights and 97219 messages whilst another station within 14Km has more flights but less messages, what does this denote, please?

Thanks in advance for any advice.

Kev

As long as we do not know the details it’s a mission impossible to tell you the reason.
If the station is using different equipment (e.g. an Airspy Receiver) then the numbers would be completely different. Airspy is well known to have double the message/position rate than a normal RTL dongle.
Maybe he has a larger or different range etc.

Friend of mine is operating a receiver with similar hardware approx 50 miles away. Every day my number of aircraft is higher, but my number of positions received/reported is lower.

You only need one valid message to ID an aircraft.
Your message count depends on a high confidence of each message.
Strong local signals, distortion in your own system, multipathing etc. can all contribute to data corruption leading to poor message count.
Simply having a poor view of the sky will have a dramatic effect.

Deleted - contained errors others corrected below.

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Beside the messages and aircraft counters, FA also have a “positions reported” counter in the stats. So there’s a third value to consider :slight_smile:

You didn’t specify what you are talking about exactly.

Please elaborate on which statistics you are referring to. (i get the impression you are talking about FA stats pages).

FA stats pages … well i’m not sure i can find the discussion about this.
You need a well established position for an aircraft, then FA will count 1 posiiton every 10 seconds for aircraft above 10000 ft, 1 position every 5 seconds for aircraft below 10000 ft.
It’s sth like that.

Now depending on how well you receive in all directions, you see aircraft for longer getting more positions per aircraft.

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That’s good information, thanks
I was asking myself already how that position count comes together.
I didn’t find a relation so far to the message count coming from the receiver

I’m not completely certain, that’s as i recollect @obj describing the logic.
Can never find the original thread when the question comes up.

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The report frequency logic is… involved. Code is here: https://github.com/flightaware/dump1090/blob/master/net_io.c#L2228

The varying report rate means that the position count on the FA stats page is not hugely useful for global comparisons since the rate depends a lot on the type of traffic seen.

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