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This is a Mode S multilateration server that is designed to operate with clients that do not have synchronized clocks.

It uses ADS-B aircraft that are transmitting DF17 extended squitter position messages as reference beacons and uses the relative arrival times of those messages to model the clock characteristics of each receiver.

Then it does multilateration of aircraft that are transmitting only Mode S using the same receivers.


It is important that you read this section before using or modifying the server!

The server code is licensed under the Affero GPL v3. This license is similar to the GPL v3, but it has an additional requirement that you must provide source code to users who access the server over a network.

So if you are planning to operate a copy of this server, you must release any modifications you make to the source code to your users, even if you wouldn't normally distribute it.

If you are not willing to distribute your changes, you have three options:

  • Contact the copyright holder (Oliver) to discuss a separate license for the server code; or
  • Don't allow anyone else to connect to your server, i.e. run only your own receivers; or
  • Don't use this server as a basis for your work at all.

The server will automatically provide details of the AGPL license and a link to the server code, to each client that connects. This is configured in mlat/ If you make modifications, the suggested process is:

  • Put the modified source code somewhere public (github may be simplest).
  • Update the URL configured in mlat/ to point to your modified code.

None of this requires that you make your server publically accessible. If you want to run a private server with a closed user group, that's fine. But you must still make the source code for your modified server available to your users, and they may redistribute it further if they wish.



It's all poorly documented and you need to understand quite a bit of the underlying mathematics of multilateration to make sense of it. Don't expect to just fire this up and have it all work perfectly first time. You will have to hack on the code.


$ mlat-server --help


You need a bunch of receivers running mlat-client:


Results get passed back to the clients that contributed to the positions. You can also emit all positions to a local feed, see the command-line help.


Mode S multilateration server







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