I’m new at this. PiAware’s been running upstairs for three days.
Today I noticed a flight I was tracking looked very different on FlightAware.com versus my local view. I’m not sure I understand why. I’ve attached two screen grabs.
Firstly, FA has tracked this as a bunch of separate flight segments, check you’re looking at the right one (you might need to look at more than one).
Secondly, this was a low flight (2000ft) so it was probably dropping in and out of your coverage, and the track you see locally is just the result of joining up the points you hear - which might skip a whole out-of-range part of the flight which is what looks like has happened with the big spike southwards in your local view - probably it flew out of range to the east, did a bunch of stuff that you didn’t hear, then came back more southerly.
Thirdly, FA does not necessarily use all the data you send, it is somewhat selective, so in general you’re never going to see exactly the same points.
I’m specifically talking about the actual location and compass orientation. They’re very different.
I can’t do much from just a screenshot of your local map unfortunately. What positions (and at what times) specifically are you looking at according to your local map?
On the flight page, you can look at the tracklog which will give you the positions/times that FA used.
Maybe I haven’t made myself clear. Those two maps are the same plane at the same (approximate) time. His flight pattern is reasonably distinct.
On the FlightAware version the ‘point’ of his flight points ESE. On my local look it points south.
It’s as if the entire displayed flight has been rotated 90 degrees or so from me to FA.
So, my question is, why?
I’m a bit curious too as I see the similarity to what you suggest, but have you noted any other flights exhibiting this behavior or is this a single anomaly?
Again, I can’t do much with this unless you give me at a bare minimum the time at which you observed the track that you have posted a screenshot of. I can see the tail number in the FA screenshot, so I can find the right aircraft at least. And ideally some coordinates; I can dig out the data which your feeder sent to FA at a particular time, but that is a summarized version of the track that is plotted locally, so it is not directly what you saw.
Once I have that I can go and find the matching track data that FA used and see what happened. But without at least a time, it’s guesswork.
First – to OBJ – I have been terribly unresponsive to you. Looking back at this thread I am not happy with my responses, so please accept my apology.
Second – to OBJ – Thank you for everything you’ve done for the community. I very much appreciate your efforts.
I had no times on those first two maps, but I’ve been able to replicate the scenario today. Both these screen shots were taken within a few seconds of each other, so Sunday at 2255z.
I looked at this flight because I heard it overhead, so my local map seems closer to reality that FA. Also, I double checked the clock and my location for accuracy.
What else can I provide you?
Ok, that helps a lot!
If you look at the FA tracklog for that flight you’ll see the data is from the FAA feed (Southern California TRACON / Los Angeles Center).
This is usually accurate for the most part, but it is also delayed by (IIRC) 5 minutes.
The data you’re seeing in dump1090 is Flightaware’s multilateration results, which are minimally delayed (a few seconds at most).
Currently, the mlat data is only integrated into tracklogs quite selectively, so you don’t see the mlat data reflected on the website.
So the reason they look different if you compare them at the same moment in time is that the website version is from 5 minutes in the past.
With the benefit of looking at it after the fact, the data you saw in dump1090 matched up fairly well with what the FAA gave us 5 minutes later.
Thank you. And, again, please accept my apology for my earlier answers.
I have looked for docs, but can’t find any. I hope you’ll answer a few questions I have.
Are ICAO numbers associated with a single transponder (tail number) or are they different with each takeoff? Will ICAO numbers become more readily associated with their planes over time?
Sometimes I will see a burst MLAT type activity. Within a few seconds a dozen or more aircraft will appear, be seen by many (is that what the seen number means) and then shortly disappear. Is this normal? Why does it happen?
How do I find where my AGC is set? Is this adjustable while dump1090 runs? I am running my Pi headless, but use ssh in to check on it from time-to-time.
Is there any local logging going on of what I’m seeing, or is it lost once I’ve sent it off and the plane disappears? There seem to be many possibilities.
Generally the 24-bit address is associated with a particular transponder / aircraft, yes. There is a mostly predictable way to go between a tail number and address for US-registered aircraft (for now, at least). This is not true for other countries, you need to look up a registry of aircraft (which may not be public) to convert between them.
The “seen” column is how long ago a message was seen from the aircraft. If it’s more than a small number, you haven’t seen a message recently. Aircraft disappear off the display after around 60 seconds of no messages. I suspect you may be hearing TIS-B messages (ground station broadcasts of local traffic) which are not very frequently sent (and I guess are sent in a burst?).
I assume you’re using the piaware sdcard image. There are some logs in /tmp/piaware.out, but this is status logging rather than aircraft data. Gain is set in /etc/init.d/fadump1090.sh (from memory)
