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List:       gpsd-dev
Subject:    Re: [Gpsd-dev] Next-generation GPSD protocol
From:       "Eric S. Raymond" <esr () thyrsus ! com>
Date:       2009-03-26 19:46:17
Message-ID: 20090326194617.GA28718 () thyrsus ! com
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(Copied to the dev list.)

Roland Arsenault <roland@ccom.unh.edu>:
> I sent this to the gpsd-dev list as a response to a message passed on by  
> Kurt Schwehr. Since the list won't accept the message from a  
> non-subscriber (not surprising!), I thought I'd send it directly to you.

I can put you in the list accept filter, if you like.  Or you could
join it and be fully part of the design discussion.  Traffic is not heavy
and tends to be high quality.  Subscription page is at:

    http://lists.berlios.de/mailman/listinfo/gpsd-dev

and I'd really like to have a representative from your research group
on board.  I think there's a lot of potential for our projects to help
each other.

> It seems like the protocol should be able to handle other NMEA devices  
> found on ships. Here are a few devices I have worked with that you might  
> want to keep in mind if you plan to expand gpsd to support devices  
> beyond gps and ais.
>
> Some ship's radar(s) are capable of reporting tracked targets as NMEA  
> sentences. This has been useful for me when I wanted information on all  
> surrounding traffic, not just the bigger AIS equipped ships.

This would definitely be in the expanded kinematic-awareness scope I'm
now thinking about.

> In addition to gps, local kinematic data may come from gyros which is  
> important on platforms where heading and course are usually not the  
> same. Some ships may be equipped with more sophisticated motion sensors  
> that combine gps and inertial sensors and report heading, pitch, roll  
> and heave in addition to integrated positioning.

This is even more clearly within scope as navigational information.

> This might be beyond the scope of gpsd, but environment sensors are  
> sometimes available that report weather observations, sea temperature, 
> etc.

Yes, this is probably out of scope.  It's location-sensitive information,
though, so we might be willing to support it if the code-complexity overhead
isn't too high and you can supply test sets (see below).

> So my suggestion would be to keep the protocol general enough to support  
> all (or most!) NMEA sentence types and data sources, even if they are  
> not related to navigation.

Here are three things you can do to make that happen:

1. Be involved in the protocol design discussion.

2. Supply us with test sets for the data sources you want supported.
   A test set must consists of pairs of NMEA sentences and human-readable
   decodings of them that I can make into regression tests.  Kurt gave
   me good test sets for AIS types 1-5, 9, and 18; I'm especially looking
   for test sets on messages 6, 7, 8, 12, 13, and 14 right now.

3. Feed us information on what NMEA 4.0 and other relevant proprietary
   standards actually say.  I haven't looked at these and won't, because 
   I'm editing documents intended to destroy their secrecy and make their
   paywalls irrelevant; I need to preserve clean-room deniability against 
   copyright-infringement claims.

If you do these things well, you'll become so valuable to the GPSD
project that I'll be strongly inclined to implement almost anything
you want.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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