Keith: In 2002 my wife and I went on the QE2 world cruise. One of the  Cunard
guest speakers was a retired Australian Navy Captain and his topic was
"Cruising from A to B to Sea". This discussion covered in part celestial
navigation and we had a group of about 50 interested persons. To demonstrate the  use
of a sextant he borrowed a sextant from the Bridge. Would you believe this!
The QE2 had only ONE sextant made of aluminium and NO vernier scale. In  other
words the nearest reading could only be made to the nearest minute. The
standard is 0.2 to 0.1 of a minute. I could not believe this and neither could  the
speaker. We were invited to the Captains dinner where we asked the Captain
about this. His comment was that his officers learned celestial during officers'
training but did not use it on the ship except to verify the ships compass
twice/day. (this is another story best left for another post). The ships
navigation was solely electronic even when anchoring at various ports. What an
eye-opener for me. Regards. Leonard Stern,  Indifference.

In a posting earlier today Leonard said:  "The ships navigation was solely
electronic even when anchoring at various ports"

I want to tell you all how important this discussion is to me.  As most of
you know I'm planning a circumnavigation.  One of the critical issues I'm
dealing with is how to back up my GPS.  I can implement a system with triple
redundancy, a scenario I can't solve is the GPS system being shut down
(national emergency...).  Does anyone know if the capability even exists to
shut it down globally?  Would the US Govt ever do that?  I know much of the
general aviation community has adopted GPS, and much like us they are
becoming dependant on it.  I can only imagine if the GPS system were ever
turned off there would be a thousand GA pilots suddenly very, very lost.

I had come to the opinion that I had to learn Celestial Navigation as the
only reasonable backup.  While I know its hard to master, I was confident I
could learn to do it, again, with the goal that it gets me close to an
island destination in the middle of the ocean.  The last post advising that
a cruise ship doesn't even practice CN left me wondering if this is still
viable?  My gut tells me sailors have been navigating by the stars for
centuries, and it is the best alternative to relying on a single source,
GPS.  I would greatly appreciate a consensus opinion on the thought this is
a skill I must have before departing.  Thanks, Scott

Scott,

I doubt that this group will arrive at a consensus opinion, I think you will have to make your own decision based on your own sense of best.

As for me, I consider a lightening strike much more likely than a long term GPS shut down, therefore I will opt for a backup or two GPS units at least one of which is protected (along with several other pieces of electronic backup) in a Faraday box, (waterproof if possible)

Regards, John Harris