Removing the worst cruft

Eric S. Raymond esr at
Sun Jul 24 05:28:10 UTC 2016

Hal Murray <hmurray at>:
> The Austron driver uses Loran.   It was unplugged in the US several years 
> ago.  I think it's still used in Northern Europe.  It may come back in the US 
> as a backup for GPS.

According to Wikipedia LORAN is dead. The principal station chains shut down
in 1979-1980. Last live use was in China in the 1990s.

What you are probably thinking of is DECCA, which was a hyperbolic radio
navigation system (very similar operating principle to LORAN but better
accuracy) deployed out of Great Britain with several station groups elsewhere
in Northern Europe.  It shut down in 2000.  A Japanese station group
continued operation until 2001.

There has been talk of reviving Loran-C, but I doubt it will happen as the
economics don't make any sense - ground-station chains just don't give enough
bang for the buck relative to a sat-nav system, especially with launch
costs dropping.

> Is this a good time to setup a procedure for second class refclocks?  Or 
> think about how to do it?

Easy stuff.  You write a little daemon that camps on the device's serial port
and delivers via SHM.

This isn't just theory.  I learned earlier today from Matt Selsky on
IRC that GPSDO vendors are *already doing this*.  I guess they noticed
GPSD and caught the lesson!

> Plan B is to not waste time on any of that and save our energy for the great 
> SHM cleanup, or whatever.

I like that plan.  Clock device drivers should be somebody else's problem.

BTW, I now think we should leave SHM as it is and write the next IPC access
to use POSIX shared memory.  While the SHM facility is widely supported on
Unix-like systems it's not really standardized enough for me to be
happy with building forward on it.
		<a href="">Eric S. Raymond</a>

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