JSON missing and Planes not showing on Map, but show on side bar with position


#1

Update: I just went to a coding group, and we looked at the JavaScript console and found a couple 404 errors. I don’t know if this is related to the problem of not all airplanes showing on the map that have position reports or not, but I’m assuming I shouldn’t be getting json 404 errors. I have removed the piaware package and reinstalled it along with dump1090-fa. I would have thought that would take care of anything. The repository I am using is Stretch except I left the PiAware repository at Jessie

json%20missing
json%20missing2

I recently did an in place update from Jessie to Stretch with the add on package. The only problem I had was having to manually copy /etc/lighttpd/conf-available packages 88 and 89 dump1090-fa to conf-enabled because it wasn’t listening on 8080 and rendering. That part is done.

Now I have noticed that airplanes are listed with location and track on the right panel but aren’t displayed on the map unless I click their entry in the table. It is most often with MLAT but ADSB is doing it too. Attached is a screenshot and you will notice the Aircraft with Positions Count doesn’t equal the airplanes with position/track data.

#mlat-results yes # using default value
#mlat-results-anon yes # using default value
#mlat-results-format “beast,connect,localhost:30104 beast,listen,30105 ext_basestation,listen,30106” # using default value

What am I missing?

Replaced screenshot with an even more extreme example, only showing 5 airplanes with positions:


#2

Sometimes I also get stuck in a tough situation like yours, and fail to debug and fix the problem.

In such tough situations I take the easy path of fresh install: burn microSD card with Raspbian Stretch image, then install Piaware & dump1090-fa package install


#3

I might do that. I didn’t know if this was a reportable bug since everything works, just not correctly. It seems odd everything works except the aircraft with positions displaying a number less than the total available in the table on the right of the screen.

I haven’t had much luck with in-place linux upgrades anyway. I thought they might have matured by now. I’m not a linux expert, just enough to get by. I see the jquery error in the JavaScript console, maybe that is where the problem is.

The group I was with are mostly React programmers anyway. Different animal.

Unless someone comes up with some easy idea, your method is probably the way to go.

Thanks.


#4

Mmmmh, the map in pictures is showing 5 planes, and above the table it says 28 planes, 5 with positions. So this somehow fits.

Also, from the 10 ADSB messages, are lot are very old, i. e. the receiver has not received another message. I am not sure at which point they are not shown on the map anymore, maybe there they are shown longer on the table. And I think not evey message contains position information, and sometimes messages are partially lost.


#5

Good catch biekerc! This fully explains the situation.


#6

If I read this right, he should have 15 planes on the map, 10 ADS-B and 5 MLAT.


#7

Sometimes MLAT planes are only shown when you click on them on the list. Also, only 4 message of those has an age of 0, the rest is not recent, so I suspect that is where the differences comes from…

This is another thread which might be useful.


#8

I also experience these issues (seeing places on the list, but no location/icon) mostly I assume this is all from bad placement of antenna.


#9

I’ll chime in with a ‘me too’ post. This has been troubling me for quite some time.

Here is my current Skyview image:

and the JSON feeding it:

{ "now" : 1525838741.5,
  "messages" : 21826,
  "aircraft" : [
    {"hex":"a1311e","mlat":[],"tisb":[],"messages":3,"seen":45.4,"rssi":-11.2},
    {"hex":"acaef6","mlat":[],"tisb":[],"messages":6,"seen":15.6,"rssi":-5.6},
    {"hex":"a3a9af","altitude":32100,"vert_rate":-3904,"track":101,"speed":474,"mlat":[],"tisb":[],"messages":90,"seen":0.4,"rssi":-3.4},
    {"hex":"abd230","lat":30.245175,"lon":-97.928943,"nucp":7,"seen_pos":30.0,"altitude":38000,"vert_rate":0,"track":285,"speed":426,"mlat":[],"tisb":[],"messages":236,"seen":0.8,"rssi":-2.4},
    {"hex":"aa700f","altitude":8975,"vert_rate":-1344,"track":256,"speed":303,"mlat":[],"tisb":[],"messages":84,"seen":1.4,"rssi":-2.6},
    {"hex":"ad6b0f","altitude":36000,"mlat":[],"tisb":[],"messages":359,"seen":1.0,"rssi":-3.3},
    {"hex":"aa2a8a","mlat":[],"tisb":[],"messages":6,"seen":280.0,"rssi":-6.3},
    {"hex":"a0ddfb","altitude":28000,"mlat":[],"tisb":[],"messages":229,"seen":1.1,"rssi":-3.8},
    {"hex":"aca01a","altitude":2925,"mlat":[],"tisb":[],"messages":157,"seen":5.7,"rssi":-1.7},
    {"hex":"a81a48","altitude":36675,"mlat":[],"tisb":[],"messages":392,"seen":0.4,"rssi":-3.1},
    {"hex":"a70523","altitude":1225,"mlat":[],"tisb":[],"messages":366,"seen":3.6,"rssi":-2.4},
    {"hex":"ad4105","altitude":10375,"mlat":[],"tisb":[],"messages":346,"seen":0.9,"rssi":-3.1},
    {"hex":"a54c60","altitude":8700,"mlat":[],"tisb":[],"messages":414,"seen":2.0,"rssi":-3.8},
    {"hex":"acc267","mlat":[],"tisb":[],"messages":171,"seen":77.2,"rssi":-4.6},
    {"hex":"a54892","altitude":7900,"mlat":[],"tisb":[],"messages":502,"seen":11.9,"rssi":-3.3},
    {"hex":"abb9b2","squawk":"1142","lat":30.043716,"lon":-97.761356,"nucp":7,"seen_pos":32.7,"altitude":16850,"vert_rate":-2880,"track":212,"speed":398,"mlat":[],"tisb":[],"messages":667,"seen":0.2,"rssi":-2.9},
    {"hex":"ad7c5b","mlat":[],"tisb":[],"messages":561,"seen":0.4,"rssi":-4.7},
    {"hex":"abdc78","mlat":[],"tisb":[],"messages":680,"seen":220.9,"rssi":-3.6},
    {"hex":"a7fa65","altitude":39025,"mlat":[],"tisb":[],"messages":791,"seen":0.0,"rssi":-3.5},
    {"hex":"abb995","mlat":[],"tisb":[],"messages":892,"seen":98.1,"rssi":-3.4},
    {"hex":"0d05ce","altitude":37000,"mlat":[],"tisb":[],"messages":1891,"seen":40.0,"rssi":-4.1}
  ]
}

Notice 4 ADS-B planes listed on the right, but only two are plotted on the map. No plane is older than 60 seconds; the last message of one of the ‘missing’ planes is only 1 second old.

Looking at the JSON, two of the entries are missing the lat-long fields so it makes sense that they can’t be plotted on the map. My question is- not being an ADS-B expert, do many jets broadcast ADS-B without locational data (my thought is no, that rather defeats the purpose). Why would my receiver see ADS-B data, but not see the locational data from those messages? I will also note that I have observed jets displaying their position on the map, only to disappear while still receiving new messages (ie, the new messages didn’t have locational data in them?)

And this missing locational data is rampant- I expect to see 25-50% of the ADS-B jets on the screen at any given point to not be plotted due to this missing data.While I realize the RSSI values are lower for the missing jets, I have many examples where values as high as -1.7 do not contain lat/long data. Can anyone shed some light as to why that data is missing?


#11

Your message rate is very low at less than 10 messages per second. You may very well not be receiving all of the position messages. Aircraft can also be ADS-B equipped and not send position data (although this is not common).


#12

Eric, thank you for the reply.

The point I was trying to make is: if there is lat/long, heading, and speed showing in the Table on the right side of SkyView then it should be possible to show on the map, stale data excepted.

Oh, sorry. I see you were replying to VANOSG. In raw capture, I see messages that only include some of the required data in the ADSB transmissions and you have to received multiple messages to get everything.

But still, the required information is available to plot on more than actually is plotted if it is visible in the table.


#13

Thanks for the reply, Eric. This capture I showed was around midnight, so I don’t know that there were that many messages to capture at that time. During peak hours, its closer to 50 msgs/sec. I have a 5db antenna on my roof with good line of sight, so I don’t know why else I wouldn’t be seeing the right data. And I again, i can see ADS-B messages (like plane adfa65 in the json & map), but there just isn’t a lat/long field there. But I’m assuming all that data is contained in each packet- does ADS-B broadcast different packets with different data types in them? ie, only every tenth packet (or whatever) contains lat/long, and the other packets contain some other type of information?

Any other thoughts as to why this scenario could occur?


#14

Mmmh,I have a flightaware atenna inside the attic, and at peak hours the message rate is 1200/s, so 50msgs/s is not an awful lot.

Maybe worth checking wether lowering the gain or adding a filter helps, in case you haven’t done this already.

I think I read somewhere that not all messages contain the location, another problem could be clipped message because the receiver is overloaded.


#15

Mmmh, that is an interesting question. I found this document, the icao doc 9924 aeronautical surveillance manual 1st edition-2011, Appendix K, it seems there are different Extended Squitter messages types:

"ES makes use of five types of squitter:
a) airborne position;
b) airborne velocity;
c) surface position;
d) aircraft ID and emitter category; and
e) event-driven.

Those are send at different rates, some twice every second, others at least once every second, if understand this correctly.

6.7.1.1
The airborne position and velocity squitters are each transmitted pseudo-randomly twice per second when
the aircraft is airborne. When airborne, the identification and category squitter is transmitted seudo-randomly once every 5 seconds.


#16

OK, so I definitely have something else going on. The antenna is directly connected to the SDR (flightaware plus, with the filter built in). I have the gain set to -10 for auto-set. I had previously had it at both 35 and 50 trying to see if that helped anything, and recently turned it to -10 for auto-set to see if that helped anything. I’m in central Texas which is not as crowded airspace as the eastern seaboard, so I just assumed 50/sec would be about right for peak.

Thanks so much for finding that document, that is extremely interesting and helpful and sheds some more light on the issues I’m having.

Open to more ideas to try!


#17

Keep in mind, -10 or automatic leads to a gain value above the max you can set manually, which is 49.x. This is due to the nature of the ADSB signals, as they are different to the TV signals these dongles were meant to receive. Try a gain script to find a good value.

Compare your message rate to those of sites near you. The number of planes seems pretty good, but the number of messages is low. E.G. there is one site close by that sees fewer planes but has almost double the number of messages.

You only see planes to the north east, and not to far away, however according to heywhatsthat.com, you have good „visibility“ in all directions, so something local must be blocking it.


#18

Thanks again @biekerc - I have a follow-on post at Issues tuning my PiAware setup If you have any thoughts to share on it over there :slight_smile: