I have an opportunity to place a feeder at an excellent but very remote location. I'd like to use a 4G dongle and rate-limited T-Mobile SIM as discussed here ... https://www.adsbexchange.com/forum/threads/a-remote-rpi.622481/ I know the data rate would far exceed the 64kB limitation of this data plan. Question: With ADSB-out now mandatory is there still a value on providing for MLAT? I'm wondering if I disallowed MLAT if I could get the data rate down so as to be feasible. Maybe someone could help me with the "big picture" here?
An ADS-B only feed is a good solution in remote locations. If you are using a normal Raspbian image, you can use this to feed ADS-B with position updates for every aircraft about every 2 seconds with the default 4 second interval settings: https://github.com/wiedehopf/lowBandwidthFeedAdsbX#lowbandwidthfeedadsbx Other details are transmitted as well, i would expect around 3 kB/s for 90 aircraft being received. That's with the default 4 second interval, it can be adjusted as desired to increase or reduce bandwidth/granularity of the data. It needs dump1090 or readsb producing data on 30005, if you aren't sure what to use, you can use this: https://github.com/wiedehopf/adsb-scripts/wiki/Automatic-installation-for-readsb The adsbexchange image can also be modified to feed low bandwidth in this fashion. Easiest way is probably to deactivate the normal feed and mlat client and use the feed script linked at the top. What do you mean with 64 kB limitation? 64 kbit/s or 8 kByte/s ? Depending on the number of aircraft visible to the feeder and the quality of reception of those aircraft, i'd expect 8 kByte/s be sufficient for around 200 aircraft in view at peak times. 64 kByte/s would probably be enough to run the normal ADS-B feed plus MLAT on top
Hi. Thanks @wiedehopf . That's very helpful. I appreciate it. I was sloppy when I specified the data rate. I meant to say 64 kbits/sec. Not bytes. That limitation is significantly lower than the upload data stream I see with my four feeders existing feeders, all of which are doing MLAT to both ADSBX and FA -- hence my reason for asking. Is my logic sound -- that MLAT is now much less valuable since ADSB has been mandatory on 01/01/20? Or, am I misreading the situation, I wonder?
Depends on what you want to track and where you are located! Anyhow with 64 kbit/s you don't want to do MLAT Note that you could feed the beastReduce data to a secondary RPi instead of adsbexchange and feed whatever from there. (secondary RPi or server having usual internet) You could even do MLAT from that machine, it wouldn't be great MLAT due to the much lower message rate of the data, but it could still work. What location are you even planning, is it lacking coverage?
Location: Coastal Georgia, USA. I'd like to "see" farther out over the ocean. I don't' want to belabor this issue but ... am I correct that since ADSB-out is now mandatory MLAT should be of minimal value -- if any? I have 4 RXs and all have some MLAT activity (at least according to FA -- the only way I can see this), although much less than last year. But there "should" be none, right?
There shouldn't be none, there is still quite a bit of airspace where you don't require ADS-B. The military also has a waiver, so if you are interested in military planes, MLAT can be useful. Most military transports seems to have ADS-B now though. You can check on the MLAT results you get back from adsbexchange as well but that's somewhat involved. On this new global webinterface from adsbexchange, you can zoom to your area and check for yellow marked planes in the list on the right: https://tar1090.adsbexchange.com/ Or you can check here where there are the mlat results only, but this page might not always be up: https://tar1090.adsbexchange.com/mlat/ Anyhow for planes far out over the ocean, MLAT would be very poor anyhow due to the relative position of all of the possible feeders on land. So go right ahead with your plans, don't let me stop you. As i said you can even feed from a local pi that gets the data from the remote pi via beastReduce. Good luck for you endeavour. If you've chosen an image you want to use and set it up locally for testing, maybe just join discord if you aren't quite clear on the details: https://discord.gg/CgJ9mf
From my point of view, apparently no one seems to bother and airlines rather pay the fine for not equipping ADS-B instead of properly retrofitting. My antenna is located in Germany, near Düsseldorf and Essen-Mühlheim airports and I see both lot's of commercial traffic going into Düsseldorf and many Cessna's doing circuits in Essen-Mühlheim and these are my stats: I've yet to see a Cessna 152/172 with something more modern than Mode A/C/S - I haven't picked up any ADS-B during the regular circuits in Essen. Approximately ~80-90% of the GA traffic I have are tracked via MLAT. For commercial traffic in Düsseldorf numbers are better, but we have many Dash 8's arriving and departing - only about 3% of those are showing ADS-B on my radar. In total numbers, of about 1600 aircrafts tracked 400 were tracked via MLAT, which gives me a total rate of 25% overall MLAT traffic In other areas numbers might differ a lot, but that's what I'm seeing. I've yet to see "ADS-B everywhere". (These numbers are up to date, I'm only considering data collected in 2020) PS: As far as I understand the legal stuff in my area, general aviation and/or light aircrafts below 5.7 tons do not require ADS-B (and 978 UAT does not exist here). However larger (commercial) airliners are required to have ADS-B now. And apparently lot's of them haven't done so. There is a two years old article saying that european airlines won't meet the 2020 requirement.
@wiedehopf I appreciate your thoughts on this. Very helpful! And, thanks, in particular, for the link to https://tar1090.adsbexchange.com/. I did not know that page existed -- nice! @Nummer378 Thanks for the "bigger picture." My understanding of the regulatory environmetn was not as good as I thought.
Two things to know about us pilots.. 1) We put damn near everything off (such as adding ADS-B to our planes), and 2) We are notoriously cheap which also feeds #1. I have a bunch of pilot friends that despite living under a Mode C veil, still haven't added it. They have to get the FAA web clearance to operate each day.. smh There are a bunch of pilots that live outside of Class B/C/D airspace and just putt putt around. Many of them won't bother adding it for $2 to 6k per plane. Also, in the US a lot of us went the 978 route as it was simple and less $ (Wingtip light or tail light units) so your 1090 only sites won't "see" us.
OK Mike. That's useful information. Since I stopped flying a few years ago I have note followed the technology very well. It was my understanding (in error) that ADSB was mandatory for all aircraft and therefor I assumed -- wrongly -- that MLAT was not to be of much use. I suppose I should build a 978MHZ feeder just so I can learn what it sees out there!
MLAT still very useful for aircraft outside of mode-c veil and below 18,000 .... and outside the USA EU
Yea, OK. That's useful information. TU. I'll keep it on for ADSBX. Trying to "shrink" the data stream a bit as I want to add a couple of feeders with 4G M2M SIMs.
Particularly many military are going to be MLAT for a while. We can use readsb beast_reduce_out to shrink the stream
Well you can't shrink MLAT unless you do MLAT with the beast_reduce on another pi with proper internet. If you are bandwidth constrained to something like 5 kB/s, you can't do MLAT period.
What I have available for the proposed location is about 55-60kb/sec. 4G cellular (M2M SIM) so latency would vary. Would that a "script install?" (Can you tell I am not a linux geek? ;<) )
kb (bits), not kB (bytes). This are bandwidth-limited SIMs which are claimed to be throttled to 64kb/sec. We've seen less, around 55-60 and also more, with peaks to 80-90, so I figure 55-60 is a fair figure to use as an estimate. So, I take it this is a "no go" OK -- that's what I needed to know. TU!
You want this and this only: https://github.com/wiedehopf/lowBandwidthFeedAdsbX#lowbandwidthfeedadsbx Before installing that, you want to install readsb or dump1090-fa: https://github.com/wiedehopf/adsb-scripts/wiki/Automatic-installation-for-readsb https://github.com/wiedehopf/adsb-scripts/wiki/Automatic-installation-for-dump1090-fa If you want to see the data on your own pi, that's where you might want to transfer the data via an SSH tunnel. This is a little more complicated compared to just feeding the data. Just hit me up on discord and i can get you started when you have the hardware.
