MLAT Priority

[k9act]

I understand how MLAT works but I am curious as to how FR24 prioritizes it vs ADSB feeds.

Is an MLAT plane always MLAT or does it change as it moves from location to location?

Does a plane with an ADSB transponder always display that way or will it change to MLAT if enough receivers report it?


Which is considered the better data? Does either have priority over the other?

Not sure how to ask this question but if that's not clear, I will try again.

Thanks,

Jack

[airnrail]

I understand how MLAT works but I am curious as to how FR24 prioritizes it vs ADSB feeds.

Is an MLAT plane always MLAT or does it change as it moves from location to location?

Does a plane with an ADSB transponder always display that way or will it change to MLAT if enough receivers report it?


Which is considered the better data? Does either have priority over the other?

Not sure how to ask this question but if that's not clear, I will try again.

Thanks,

Jack

A plane either has ADS-B or it doesn't so only those that have it will ever show up on FR24 with a feeder designation. The ones that show up as MLAT have a Mode S transponder and it supposedly takes signals from four feeders for FR24 to be able to triangulate the data. I don't know enough about the technical side of things to say for sure if an ADS-B equipped plane is detectable for MLAT purposes but I imagine that it is in some shape or form. However one thing I have unfailingly observed is that on FR24 a particular aircraft only ever shows up as one or the other, never both.

[Patrick Reeves]

Which is considered the better data? Does either have priority over the other?

I don't think that's a relevant question since the two are so different. But if you look at a log segment:

2015-06-30 14:18:01 | [mlat][i]Pinging the server
2015-06-30 14:18:01 | [mlat][i]Stats 17206570/5728
2015-06-30 14:18:03 | [feed][i]sent 61 AC in 4 packets
2015-06-30 14:18:06 | [feed][i]sent 62 AC in 4 packets
2015-06-30 14:18:09 | [feed][i]sent 65 AC in 4 packets
2015-06-30 14:18:12 | [feed][i]sent 64 AC in 4 packets
2015-06-30 14:18:15 | [feed][i]sent 63 AC in 4 packets
2015-06-30 14:18:18 | [feed][i]sent 63 AC in 4 packets
2015-06-30 14:18:21 | [mlat][i]Pinging the server
2015-06-30 14:18:21 | [mlat][i]Stats 17211372/4802
2015-06-30 14:18:21 | [feed][i]sent 62 AC in 4 packets
2015-06-30 14:18:24 | [feed][i]sent 60 AC in 3 packets
2015-06-30 14:18:27 | [feed][i]sent 63 AC in 4 packets
2015-06-30 14:18:30 | [feed][i]sent 57 AC in 3 packets
2015-06-30 14:18:33 | [feed][i]sent 63 AC in 4 packets
2015-06-30 14:18:36 | [time][i]Synchronizing time via NTP

It appears that MLAT transmits every 20 seconds, and syncs with NTP every 10 minutes, typically.
ADS-B packets are transmitted every 3 seconds. I'm sure someone will correct me here if my interpretation is wrong.

[k9act]

OK on all but one more side of the same question:

Would a plane with ADSB ever show up as MLAT?


And yet another.... if MLAT is only using no positional date, where is FR24 getting the position and altitude from?

Jack

[k9act]

I don't think that's a relevant question since the two are so different. But if you look at a log segment:


It appears that MLAT transmits every 20 seconds, and syncs with NTP every 10 minutes, typically.
ADS-B packets are transmitted every 3 seconds. I'm sure someone will correct me here if my interpretation is wrong.

Perhaps I am missing something but on the logs I have looked at, I see no MLAT entries. Just feed, stats and sync. Here is a small piece from today:

2015-06-30 10:20:53 | [feed][i]sent 18 AC in 1 packet
2015-06-30 10:20:57 | [feed][i]removed 1 of 24 AC
2015-06-30 10:20:58 | [feed][i]sent 14 AC in 1 packet
2015-06-30 10:21:03 | [feed][i]sent 16 AC in 1 packet
2015-06-30 10:21:08 | [feed][i]sent 13 AC in 1 packet
2015-06-30 10:21:13 | [feed][i]sent 13 AC in 1 packet
2015-06-30 10:21:18 | [feed][i]sent 14 AC in 1 packet
2015-06-30 10:21:23 | [stats][e]Cached feed_id=7083 for network T
2015-06-30 10:21:23 | [stats][i]sent 1127 bytes
2015-06-30 10:21:23 | [feed][i]sent 16 AC in 1 packet
2015-06-30 10:21:28 | [feed][i]sent 15 AC in 1 packet
2015-06-30 10:21:33 | [feed][i]sent 14 AC in 1 packet
2015-06-30 10:21:38 | [feed][i]sent 15 AC in 1 packet
2015-06-30 10:21:43 | [feed][i]sent 16 AC in 1 packet
2015-06-30 10:21:48 | [feed][i]sent 15 AC in 1 packet
2015-06-30 10:21:49 | [feed][i]removed 1 of 25 AC
2015-06-30 10:21:53 | [feed][i]sent 13 AC in 1 packet
2015-06-30 10:21:59 | [feed][i]sent 13 AC in 1 packet
2015-06-30 10:22:04 | [feed][i]sent 12 AC in 1 packet
2015-06-30 10:22:05 | [feed][i]removed 1 of 25 AC
2015-06-30 10:22:09 | [feed][i]removed 1 of 24 AC
2015-06-30 10:22:09 | [feed][i]sent 13 AC in 1 packet
2015-06-30 10:22:14 | [feed][i]sent 11 AC in 1 packet
2015-06-30 10:22:17 | [feed][i]removed 1 of 23 AC
2015-06-30 10:22:19 | [feed][i]sent 12 AC in 1 packet
2015-06-30 10:22:21 | [feed][i]removed 1 of 23 AC
2015-06-30 10:22:24 | [feed][i]sent 12 AC in 1 packet
2015-06-30 10:22:29 | [feed][i]sent 10 AC in 1 packet
2015-06-30 10:22:34 | [feed][i]sent 13 AC in 1 packet
2015-06-30 10:22:37 | [feed][i]removed 1 of 24 AC
2015-06-30 10:22:39 | [feed][i]sent 12 AC in 1 packet

js

[Patrick Reeves]

Is that log from T-KRFD1? T- feeders don't send MLAT. An FR24 receiver with GPS antenna is required.

[k9act]

Is that log from T-KRFD1? T- feeders don't send MLAT. An FR24 receiver with GPS antenna is required.

Funny you should mention that. I just noticed the different letters in front of the alias call was and going to ask what they meant.

So what do they mean?

js

[Patrick Reeves]

http://forum.flightradar24.com/threads/6789-Flightradar24-Feeder-Chat/page95

[SoCalBrian]

If something changed on the FR24 end. I still believe T-Feeders do send MLAT to FR24 if they use the Radarcape box with the MLAT option turned on.

Is that log from T-KRFD1? T- feeders don't send MLAT. An FR24 receiver with GPS antenna is required.

[North Borneo Radar]

K9act,

If you are using a rpi 2 / b+ , FR24 announced yesterday they are trialling a beta feeder software for MLAT.

Please see link http://forum.flightradar24.com/threa...r-Raspberry-Pi

Please Note however this is a beta test and you won't notice any immediate result on FR24 map.