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Fred H., you wrote:
"It's very nice to have one's faith in the utility of sextants on small
boats restored now and again.  I wonder whether Frank were trolling for such
a response!"

Not a bit, Fred. My point is merely that the best backup for a complicated
GPS "system" aboard a boat, with all its complexities and risk of electrical
failure, is a simple well-protected handheld GPS. We all enjoy celestial
navigation here, no doubt about it. But its value for backup navigation is
quite limited -- it takes specific education, skill, practice; it only works
when the weather cooperates; its accuracy is much less than GPS; it requires
special tables and a delicate instrument; it requires a functioning watch,
typically electronic, for a complete fix; etc.

I've been trying to think of people who use handheld GPS units in stressful
marine conditions. It occurred to me that sea kayakers often use GPS units
and they get dunked quite regularly. I also learned about a neat little gps
sport called 'speedsurfing'. These folks are wind surfers who collect speed
records using GPS units, usually attached to their wrists or ankles. A very
wet environment. I doubt they would survive a lightning strike (!), but such
applications may serve to remind people that many of these devices are now
designed to be quite robust.

So what would make a good backup nav system aboard a small boat? I suggest a
waterproof handheld GPS unit, capable of floating, as many are, with a dozen
spare batteries (I would think a unit that takes standard AA batts would be
preferable here) kept in a waterproof pouch and all that stored in a sturdy
metal box to protect against lightning strikes and lightning-induced EMP.
Throw in a small-scale paper chart if you like. Also, there should be very
simple printed instructions on a laminated card so that a layperson can use
it in an emergency and know how to operate the unit and not use up the
batteries too quickly.

So where's the sextant then? Well, gee, that's your PRIMARY navigation
system. Use that every day and impress your friends. And of course, in the
highly unlikely event of the disabling of the GPS constellation of
satellites, then you'll have celestial as a backup for the backup.

 -FER



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