[time-nuts] Can eloran Backup GPS?

Poul-Henning Kamp phk at phk.freebsd.dk
Sun Sep 9 11:20:45 EDT 2018

In message <3d2ae1be-927a-574a-e7f0-c7d2d289dc39 at earthlink.net>, jimlux writes:
>On 9/8/18 4:52 PM, paul swed wrote:

>I suppose you could have a low rate network (i.e. not "the internet") 
>and for the most part, the propagation corrections (whether using 60kHz, 
>Loran, Omega, or GPS) can be done with "climatology" - time of day and 
>time of year.

Transmitting real-time corrections is not the problem, coming up
with them in the first place is.

One of the reasons eLoran failed to go anywhere in europe is that
tests showed that modern container freighters are big enough to
'relevantly disturb Loran-C'.

Nobody has a clue how you could possibly measure the necessary
real-time corrections for narrow and heavily trafficked straits
like as The English Channel, The Great Belt etc.

For big/expensive boats, INS/IMU is the goto-solution, at around
$20-50k a piece, depending on specs.

In difference from anything relying on radio signals from people
you can maybe trust some of the time, INS/IMU is entirely on-board,
which can lower your insurance premiums if you sail certain parts
of the world.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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