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Transponder over network

OpenRadar is a standalone radar screen which connects to the FlightGear multiplayer servers. It is currently being developed.

Re: Transponder over network

Postby Secret_Hamster » Thu May 16, 2013 10:33 pm

I've been reading up on transponders, their use. I've also been listening to Newark Liberty airport alot recently and listening in to their use

Effectively there is an area in which all squawk codes are managed to be unique. On crossing those borders you will get reassigned a squawk code. So typically it goes like this.

You take off, climb and enter Approach airspace. At this point you will be assigned a squawk code. You callsign is entered into the "management system" along with the squawk code. Now whenever you are handed over, the first thing they seem to do is announce what they are squawking. So the management system could be anything, a piece of paper, a fully centralised database, whatever system their is. Controllers are also quite free to ask the pilot to change the squawk code too.

So the issues we have here are.
1) We pretty much are going to need all aircraft to have working transponders in. In real life normally one of the criteria of entering controlled airspace (A-D) is a working transponder. So I'm thinking we need a OR mode to switch to "no callsign displayed unless squawk entered". So up until then we will need to have a hybrid of real life and what we have now.
2) As we keep seeming to bring up, there needs to be some communication or centralisation going on if a pilot is to keep a sqwark code between ATC controllers. This is something to thing about in that project, but for now I think it can be a procedural thing. To me IRC seems to be the perfect medium for that. say #ATC-EUROPE or the existing #ATC though we do chat alot about anything in there.
3) Ident is a 13th bit, from what I can tell on most systems it "blooms" the contact on the radar so it's easier to find. I think a similar method would work for OR. Make the text bold or bigger I don't think different colours are needed. The flight strip should be alterable to have either call-sign or squawk or both.

The tasks then for Wolfram depend on how realistic we want to be. Currently pilots have enough difficulty with fgcom, flying in controlled areas, and using the correct terms on FGCOM. Adding the requirement for squawk codes could currently be a step too far. However, I'd like to see us in the ATC/OR community ready for them and the more advanced among us give it a try.
So currently we should be looking at this hybrid mode. Currently does anyone know what happens if two users have the same callsign? Squawk codes would help on that if the system does die have an issue with identical call-signs.

Finally, I'm not actually sure what this pof file is for. Could someone try to explain it a different way, as I'm not getting it.
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Re: Transponder over network

Postby Johan G » Sun May 26, 2013 12:21 am

Working on the aircraft type and code mappings I have run into what first seemed like one one of the inconsistent and less documented areas of FlightGear. It's the aircraft type as given by the packets from the FlightGear multiplayer server software (fgms).

I was quite sure that I should map to Aircrafts/Name of aircraft/<Name of aircraft>-set.xml, as that is the name that I have seen most often, and what seems to set apart different versions of an aircraft available in one package (see Aircraft-set.xml on the wiki), but asking wagnerw it seems that the multiplayer system instead uses Aircraft/Name of aircraft/Model/<Name of arcraft>.xml, though it is not fully clear from the fgms documentation (see mpmessages.hxx File Reference):

#define MAX_MODEL_NAME_LEN 96

Maximum length of a model name, eg /model/x17/aero-123.xml.

Definition at line 78 of file mpmessages.hxx.


Looking at the client side instead then. Browsing through multiplaymgr.cxx on Gitorious (not easy for me, I can hardly even do a "Hello world!" in C/C++) I saw a reference to the property /sim/model/path, which when searched using Google lands me in Howto:3D Aircraft Models on the wiki. All this gets me to the below conclusion:


Apparently the name of the aircraft as given through the multiplayer system is either:
  1. The path to the 3D model
  2. The path to the property-list xml file with the animations and the path to the 3D model.
The path to either file can often but not always be given in the Aircraft-set.xml file.

Code: Select all
<PropertyList>
<sim>
  <model>
    <path>Models/my-cessna.ac</path>
    <texture-path>./Textures</texture-path>
  </model>
</sim>
</PropertyList>

Code: Select all
<PropertyList>
<sim>
  <model>
    <path>Models/my-cessna.xml</path>
  </model>
</sim>
</PropertyList>


Maybe this is available in $FG_DATA/Docs/README.multiplayer on Gitorious, but I get an http 500 "Internal server error", and I doubt the info is there anyway. :|


Figuring all this out took me about 2 1/2 hours. :(

This will be more difficult than I initially thought. :roll:

EDIT: I think the current solution initially was there for performance reasons. Why not skip parsing Aircraft-set.xml and just load the model at once?
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Re: Transponder over network

Postby wagnerw » Sun May 26, 2013 8:16 am

I guess the path is there to allow individual 3D models for the contacts...

In OR the mapping input for the aircraft is the data transferred via model, stripped down to the content between the the last path separator and the appendix '.xml'

So
Aircraft/c172p/Models/c172p.xml
is stripped down and made uppercase to:
C172P

The replacement rule in data/aircraftCodes.txt modifies it to the ICAO code:
C172

So the rules we need are for example like this:
C172.* => C172

More examples are in the mapping file in GIT, where I tried to add the most used aircraft...
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Re: Transponder over network

Postby Gijs » Sun May 26, 2013 8:20 am

Thinking about it, you'd also need some way to filter out dual control aircraft (well, combine them into one radar contact). Displaying two or more players at exactly the same position would needlessly scare the controller :-)
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Re: Transponder over network

Postby wagnerw » Sun May 26, 2013 8:32 am

I thought about that already. Both contacts are often displayed with a one step distance. To do so I need to know, which contacts are linked together. As much as I know, this information is not transmitted via MP protocol. Maybe someone can add it?!!

I follow with OR as soon as this is done...

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Re: Transponder over network

Postby Secret_Hamster » Thu May 30, 2013 6:03 am

I know I'm not contributing code in all this (well luckily for you guys not at the moment)

But the whole MP protocol needs looking at. To me there should be a property in the *.xml or a *-set.xml to actually set the aircraft type. Perhaps two a long and a short (the short being an icao code).

Dual control is an interesting one, from the sensible point of view only the pilot in control should transmit any data to the FGMS on location, the other players/characters on the plane should be talking to main pilot either directly or through some intermediary.

But again this is not using current methods. I just wish I had more time and expertise to contribute.
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Re: Transponder over network

Postby wagnerw » Thu May 30, 2013 7:32 am

What I could do is to hide the co-pilot, recognizing him by his aircraft. The copilot's chat needs to be mapped to his pilot (main callsign), but I will run into trouble to recognize the pilot and the naming of the copilot aircrafts is different, almost from model to model and some seem to support this feature without changing the model by configuration only.

If someone could add the "master" aircraft to MP protocol, I could implement the hiding and the mapping, so from OR side, it would work.
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Re: Transponder over network

Postby F-JJTH » Thu May 30, 2013 10:09 am

Hi all,

Just to inform you that transponder over network is now 100% working since some days in FG GIT and it will be available in the next FG release.

@Wolfram: Is it fully working for OpenRadar ?


About dual control I would say : aircraft designers must use a conventional naming - myAircraft for pilot, myAircraft-copilot for copilot, in this way you can easily skip the copilot.

Cheers,
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Re: Transponder over network

Postby F-JYL » Thu May 30, 2013 10:20 am

Do you know if it is available for all planes ?
I am using the 777 and I do not see any transponder, but it is available in the radio settings menu when I use the C172P
Is there any documentation associated with this feature ?
Thanks for your work.
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Re: Transponder over network

Postby F-JJTH » Thu May 30, 2013 1:29 pm

Transponder is available for all planes through the Radio setting dialog.
If you want create a transponder instrument you can have a look at the Instruments-3d/KT76A, I think this one can be considered as a source of documentation.

Cheers,
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Re: Transponder over network

Postby wagnerw » Thu May 30, 2013 3:40 pm

Hi,
The updated OR version in Wiki features a simple transponder support, compatible to the current FGFS implementation. This feature is in the prototype phase because there have been no clear definitions how this should work in OR. Please see the wiki page: http://wiki.flightgear.org/OpenRadar:_Transponder

Clement: When we have a dual controlled aircraft in our range, we get two separate, unlinked contacts from the MP server. Such an aircraft should have only one contact point in radar and only one flight strip. Also chat messages of the two pilots should appear as if they are sent from one.
The best and most consistent way I see is to have a short string in mp protocol, that is filled only for the copilot and contains the pilots callsign. I will do the rest...

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Re: Transponder over network

Postby Johan G » Sat Jun 01, 2013 9:05 am

This is not a request for the military transponder modes, I just want to clarify one thing.

When I was looking around for information about the transponder modes, I found it easy to find what modes there where, except for that many sources only mention them as A, C and S as in the first post (I guess I have seen too much of Mr. Spock to accept that as anything but in-precise :wink: ). However there was some confusion about the use of the older military modes, 1 and 2.

Some sources gives the impression that mode 2 is only used on ships (as in sea-going vessels). Most sources (including data sheets, aircraft specific sites like F-15E.info and Wikipedia) mentions that while mode 1 (00-73, 64 codes, though it seems some transponders only supports 32 codes, 00-40), often called "mission code", can be set in the cockpit, mode 2 (0000-7777, 4096 codes), often called "unit code", only can be set on ground (except for transport aircraft) and more or less represents the individual aircraft (it seems it is often set on the transponder itself in an avionics bay).

I would guess that during operations fighters would use mode 4 instead of mode 1, 2, 3/A or 3/C as mode 4 seems to only respond to a an encrypted pulse, in essence only the right equipment would be able to extend its radar range to and/or get any information about a mode 4 equipped aircraft, except for position and possibly approximate altitude.


Also, I noted that interceptors turn off mode 3 when approaching supposed civilian aircraft. Why? Because they would otherwise trigger the TCAS to have the crew do evasive manoeuvres not suitable for this particular situation. While they of course would not be able to escape, there will be an increased risk of collision, not to mention the discomfort for the passengers.
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Re: Transponder over network

Postby Omega » Sat Jun 01, 2013 6:13 pm

I dislike that a newly assigned squawk code is automatically send via a text message for several reasons... The assigned squawk code can appear on the flightstrip only.
Next thing that I will suggest for the next release is something that bugged me quite a bit lately. When I select the active landing rwy the blue rwy centerline appears, the problem with that is that it extends up to 100nm which obviously is a waste since most ILS transmitters are limited to an 18nm range. I don't think anyone would vector a plane for a 100nm final just to find out that the ILS doesn't work :? . So my suggestion is to reduce the centerline's length down to 18nm.

I'm still looking for the changes with the tags to get in effect since they will significantly reduce the size of the tags.
Even though I'm not so good with picture editing, I tried to create a few examples to show the difference:

Before (current state):
Image

After (changes applied):
Image

And in case we can't make the ICAO code displayed like that then the final result should look something like this:
Image

I also placed the arrow right next to the altitude, but it can still be kept just like how it is if that's not possible.
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Re: Transponder over network

Postby wagnerw » Sun Jun 02, 2013 7:49 pm

Omega wrote in Sat Jun 01, 2013 6:13 pm:I dislike that a newly assigned squawk code is automatically send via a text message for several reasons... The assigned squawk code can appear on the flightstrip only.

Please be so kind an explain why! I don't understand, that you don't want it to be transferred. Even when you say it, the contact will have less issues to understand, if he gets it parallel.
When I select the active landing rwy the blue rwy centerline appears, the problem with that is that it extends up to 100nm which obviously is a waste since most ILS transmitters are limited to an 18nm range. I don't think anyone would vector a plane for a 100nm final just to find out that the ILS doesn't work :? . So my suggestion is to reduce the centerline's length down to 18nm.

Maybe 100 NM is too far, but this feature exists by purpose, to allow an early alignment with the runway. As this feature came out of the community, I cannot change it easily. Please discuss it!
I'm still looking for the changes with the tags to get in effect since they will significantly reduce the size of the tags.

You seem to have missed the new feature: Map - Datablock layout - Simulation will bring you closer to VRC.

If you could test squawking, I wonder why you missed it. The squawking feature is enabled in simulation and pure simulation layout only. The traditional layout will stay, because there is a number of people who like it very much.
We may improve the simulation layouts and even try to add a new one, but, I need to get a full definition of when to display what.

Anyway, thanks for your feedback!
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Re: Transponder over network

Postby Omega » Sun Jun 02, 2013 8:19 pm

1. I may click "assign squawk" by mistake.
2. I may need to include additional instructions to the squawk assignment in the same message (e.g.: Reset transponder, squawk 0351 - Cleared to xxxx via x squawk 1234 - squawk 0123 and ident).
3. I may need to change to a different squawk code, either because the squawk code range values were incorrect or some other aircraft was already assigned the same squawk code.
4. An aircraft may be communicating via voice (FGcom, mumble etc). Therefore, sending the squawk code over text would be considered as something unnecessary.

Maybe 100 NM is too far, but this feature exists by purpose, to allow an early alignment with the runway. As this feature came out of the community, I cannot change it easily. Please discuss it!

There is already a simple ruler feature for that but my main concern is that it doesn't look professional enough, there is a reason why they don't have center lines extending up to 100nm in vatsim or any other real life radar scope. I'd rather have the aircraft just proceed direct to the airport or a navaid and then be vectored for final at a good range for the ILS. If they are on a STAR that would be much better.

I didn't test squawking yet but thanks for letting me know.
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