Help Interpreting Flight Track Info

FlightAware ADS-B Flight Tracking
1

Hello,

I provide feeds locally, to FlightAware, and ADSB Exchange.

Yesterday, I was watching an aircraft doing touch and goes. The tracks shown on my local dump1090-fa feed are slightly different than the racks shown on the flight history shown here: – https://flight-data.adsbexchange.com/map?icao=AD4643&date=2019-03-19

The tracks on my local feed are rounded where as those shown on the ADSB-Exchange history are straight lines from point to point.

So, what is going on? Does dump1090-fa interpolate the curves between those dots or do those dots on the history page represent only a few of the data points that dump1090-fa uses to draw the paths taken by an aircraft?

Thanks for any insight provided.

John Ullom

2

Saving more granular data would take more space, slow down the database.

If you receive all packets, ADS-B from every aircraft provides you with 2 aircraft positions per second as far as i know.

dump1090-fa does no interpolation.

The dump1090-fa history when you first load the web page also is not as fine grained, i believe the data points are 30 seconds apart.

Even the live map doesn’t display all positions you receive (provided the altitude stays the same).
So you can make the tracks even more precise if you modify your web interface :wink:

I’ve also moved the thread into the Flight Tracking category.

3

Thank you!

So the dots on the ADSB are only showing selected based on some sort of algorithm. Per your explanation, there is a data point created every 2 seconds.

What I would hope then to do is:

A) Create my own database of positions received.

B) Create Flight History Displays using the data in my database.

With that in mind, I am hoping somebody can point me towards a tutorial, or a the right sections of code in dump1090-fa, or anything else that will help me deduce how to get started. My coding skills are such that I can usually figure out what to do but not how to get started.

4

No i talked about ADS-B which is the protocol the aircraft sends you information, the position is sent twice per second.

ADSBexchange probably stores longer intervals than 2 seconds, looks like a minimum of 6 seconds.

Only project i know about in regards to what you are asking for is this:
GitHub - Ysurac/FlightAirMap: Open source project displaying live aircrafts, ships or trackers on 2D/3D map. Browse through the data based on a particular aircraft, airline, airport, tracker or vessel to search through the database or see extensive statistics. Can use ADS-B in SBS1 format (dump1090, Radarcape,...), VRS, VA (VATSIM, IVAO whazzup.txt, phpvms,...), ACARS (acarsdec, acarsdeco2), APRS, AIS as datasource.

Maybe others know of some other software.

5

FWIW, the FlightAware server-side tracks typically store a point every ~30 seconds, but then the track is splined to smooth it out for display.

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