On a trip to Hawaii I had two GPS units completely fail and a third just
died for lack of enough batteries. Not to worry even with some rust to dust
off my cursory skills I found when cross checking with a passing ship my
poor celestial skills had me located fairly close on the chart to where I
was on the planet. For a good start I had maintained an accurate DR plot
and so had a good start point when the 'lights went out'.

If you want real backup take the time and trouble to become acquainted with
real navigation. Each type and style mutually supports the others at best or
at worst stands alone. That starts with Coastal Navigation and Piloting,
Deduced Reckoning, if you are going off shore add in Celestial of course,
and then there's the understanding of natural things usually referred to as
Polynesian style navigation and finally, last but not least the age of
tricks of seafarers embodied in such books as "Emergency Navigation." Those
who live by the "AA" will surely meet their well deserved fate by the lack
of the "AA". Or you could just stay on your Bayliner and pretend a lot.
It isn't that hard to learn and beats watching Seinfeld re-runs ad nauseum.


MSK