Gene, on Guenevere when we are out we have a lost plotter plan.

During any open water passage we use our Standard Horizon chart plotter. BUT we also put pencil to paper chart on our Yoeman plotter every 30 min (max.).

Next, we have one of the small e-Trex GPS and a digital watch spare. We put that in a storage box that I made into a “Faraday cage”. Mostly to protect it from a lightning strike, but that's just an EMP by another name.

We carry a sextant, set of tables and almanac.

The low cost watch I use is digital, it has a solar cell in it for charging, and gets an auto time hack when within range of one of the stations.

When my mind wanders to the "post Armageddon" thoughts, on those long night watches, I have come to some conclusions.
If it's a man made event, there are MANY GPS sats up there and a few EMPs would not likely take them all out. And the main concern is more of where to go. Not so much as how to nav to get there.

If it's a natural event, all the navigation stuff we have aboard may not be of ANY use. If the land masses move, or change, it's back to the Ferdinand Magellan type of navigation.. AND, it may most likely be useless any way.....

But back to the main question...... Joshua Slocum had an old wind-up tin clock....

Greg