MLAT and Piaware

[obj]

@whacky

In a different application, I know of RF time-of-flight measurement/MLAT using sequence number. So I am trying to deduce whether ADS-B MLAT relies on sequencing. (Timestamp is just one possible sequence.)

You say “ADS-B mlat” but FWIW we don’t do mlat on ADS-B messages. (I mean, you could - but given they already contain a position it’s not very useful). They’re used for synchronization only.

I have posted at length about the details of how the mlat system works in the past so I’m not going to go into it again (I’m sure google will find it, or look at mlat-server on github) but the short version is that position messages from ADS-B equipped aircraft are used as a common reference to synchronize the free-running sample clocks. Typical precision is around 0.5us. Then we use the synchronized clocks to do TDOA multilateration on non-ADS-B messages. The system time of the Pi is irrelevant and is not used.

[abcd567]

@wiedehopf

If you install it without having data available or use the wrong options it uses the internal one i believe.

@abcd567

I will check tonight by writing a fresh raspbian image on a spare microSD card, and installing only rbfeeder and will not make any changes to its default setting and will see what happens.

OK, wrote raspbian image to spare microSD card, installed rbfeeder only, and checked. Got this:

Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]  Network-mode enabled.
Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]                  Remote host to fetch data: 127.0.0.1
Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]                  Remote port: 30005
Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]                  Remote protocol: BEAST
Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]  System: raspberry
Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]  Start date/time: 2020-11-07 07:46:56
Nov 07 07:46:56 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:56]  Socket for ANRB created. Waiting for connections on port 32088
Nov 07 07:46:57 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:57]  Connection established.
Nov 07 07:46:57 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:57]  Connection with RadarBox24 server OK! Key accepted by server.
Nov 07 07:46:59 raspberrypi rbfeeder[1338]: [2020-11-07 07:46:59]  Can't connect to external source (127.0.0.1:30005). Waiting 5 second...
Nov 07 07:47:39 raspberrypi rbfeeder[1338]: [2020-11-07 07:47:39]  Can't connect to external source (127.0.0.1:30005). Waiting 5 second...
Nov 07 07:47:44 raspberrypi rbfeeder[1338]: [2020-11-07 07:47:44]  Can't connect to external source (127.0.0.1:30005). Waiting 5 second...
Nov 07 07:47:49 raspberrypi rbfeeder[1338]: [2020-11-07 07:47:49]  Can't connect to external source (127.0.0.1:30005). Waiting 5 second...

Rebooted, waited five minute, then checked, again above noted output.

Edited file /etc/rbfeeder.ini & changed line

network_mode=true
to
network_mode=false

Restarted, and got this output

Nov 07 07:49:46 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:46]  Starting RBFeeder Version 0.3.5 (build 20200727132301)
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:46]  Using configuration file: /etc/rbfeeder.ini
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:46]  Network-mode disabled. Using local dongle.
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: Found Rafael Micro R820T tuner
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:46]  System: raspberry
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:46]  Start date/time: 2020-11-07 07:49:46
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:46]  Socket for ANRB created. Waiting for connections on port 32088
Nov 07 07:49:46 raspberrypi rbfeeder[1403]: Allocating 4 zero-copy buffers
Nov 07 07:49:48 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:48]  Connection established.
Nov 07 07:49:48 raspberrypi rbfeeder[1403]: [2020-11-07 07:49:48]  Connection with RadarBox24 server OK! Key accepted by server.

 

Installed piaware and configured it as follows:

sudo piaware-config receiver-type other   
sudo piaware-config receiver-host 127.0.0.1   
sudo piaware-config receiver-port 32457   
sudo piaware-config mlat-results-format beast,connect,localhost:32004
sudo systemctl restart piaware   

 

Now Piaware is getting data from rbfeeder

Nov 07 07:58:05 raspberrypi sudo[4099]: pam_unix(sudo:session): session opened for user root by (uid=0)
Nov 07 07:58:05 raspberrypi sudo[4099]: pam_unix(sudo:session): session closed for user root
Nov 07 07:58:05 raspberrypi piaware[4068]: ADS-B data program 'rbfeeder' is listening on port 32457, so far so good
Nov 07 07:58:05 raspberrypi piaware[4068]: Starting faup1090: /usr/lib/piaware/helpers/faup1090 --net-bo-ipaddr 127.0.0.1 --net-bo-port 32457 --
Nov 07 07:58:05 raspberrypi piaware[4068]: Started faup1090 (pid 4108) to connect to rbfeeder
Nov 07 07:58:05 raspberrypi piaware[4068]: UAT support disabled by local configuration setting: uat-receiver-type
Nov 07 07:58:05 raspberrypi piaware[4068]: mlat-client(4098): Beast-format results connection with ::1:32004: connection established
Nov 07 07:58:06 raspberrypi piaware[4068]: piaware received a message from rbfeeder!
Nov 07 07:58:08 raspberrypi piaware[4068]: piaware has successfully sent several msgs to FlightAware!
Nov 07 07:58:37 raspberrypi piaware[4068]: 25 msgs recv'd from rbfeeder; 25 msgs sent to FlightAware