Re: [gpsd-users] New client and ADS-B question

[Cédric]

Hello Eric,

Thanks for answering my question personally!

I personally don't have an ADS-B receiver yet. But if I can be of help
and progress could be made for GPSD, then I might look forwards into
buying one.

The question I haven't succeeded answering yet is what kind of (serial
line) protocol ADS-B devices use, and most importantly, if it is a
standard protocol or if each brand has its own proprietary protocol.
Also, from what I'v been reading here and there, I have the feeling that
we're not talking of anything as "simple" as a NMEA0183-like protocol.

On their blog, the manufacturer of the apparently very cool GNS 5890 USB
receiver claims that they're open to the community
(http://www.blog-ads-b.gns-gmbh.com/?page_id=5#comment-4) but I could
not fight any relevant information on the link they point to
(http://www.5890.gns-gmbh.com/Service.html). The fact that (Windows)
common ADS-B application seem to support it may point to some "de facto"
common protocol (SBS-1?).

Besides, FlightRadar24 just announced a Linux version of their "feed"
software
(forum.flightradar24.com/threads/4270-Linux-feeder-software-for-Flightradar24),
but it is yet unclear with what devices/protocols it will work... and
unfortunately, it seems closed-source (...).

Going through the latest posts about the latter, I stumbled on
http://www.homepages.mcb.net/bones/SBS/Article/Barebones42_Socket_Data.htm
, which details the basics of the (Kinetic Avaiation's) SBS-1 "socket"
protocol.
>From which I stumbled on http://www.kinetic-avionics.com/, which says
that their latest SBS-3 is able to decode data both to ADS-B and AIS
mode, from which I (maybe erroneously) conclude: 1. ADS-B seems a
standard message protocol in itself; 2. ADS-B data can somehow be fitted
in the AIS protocol (though I fear with serious limitations)

I also went through:
http://www.hamradioscience.com/the-rtl-2832u-sdr-and-ads-b/
https://github.com/bistromath/gr-air-modes
Which seem the most low-level yet most interesting links on the subject.

Finally, googling for "ADS-B + Linux" raises many mentions of the
microADSB receiver. I haven't suceeded yet in finding relevant
information on that device.

So:

Do you have any idea at which "level" we should try to get into ADS-B?
(I mean should be try at the "lowest" possible level, based on what
could be "contributed" by https://github.com/bistromath/gr-air-modes or
should be satisfy ourselves with "higher" - maybe manufacturer-dependent
- level like SBS-1)

Do you think its worth my investing in a MicroADSB or a GNS 5890 ADS-B
receiver and that we try to get something out of it along with GPSD?

Best,

Cédric


On 29/09/12 20:25, Eric S. Raymond wrote:
> Cédric <address@hidden>:
>> Now, I see ADS-B support has been mentioned in
>> http://lists.nongnu.org/archive/html/gpsd-dev/2012-06/msg00038.html but
>> could not find any further information in this regards. May I inquire
>> what is the status and your plans in regards with ADS-B support?
> It's something we'd like to do someday.
>
> What we'd need to go from wish to code is ADS-B test pairs.  A test pair
> would consist of 
>
> (a) A sequence of ADS-B packets in whatever native format they use - binary 
> blob, AIVDM/AIVDO-style armored packets, whatever.
>
> (b) A known-good decoding of that sequence into an annotated textual form
> that I could massage into some sort of conformable JSON.
>
> We'd also need a pointer to the specification for the format used in (a).
>
> With these things, I could probably go from zero to a testable ADS-B 
> driver in time on the close order of a week.