Quote: No matter how good you were on your precious day skipper course trusting an EP over a GPS position is just a joke.
Isn't this similar to the LR thread ... it is unlikely to happen and you can have a spare at hand quite easily ... chances are that the GPS network won't let you down ... however it would be sensible to know where you are if it does ...
As for loosing the plotter to start with - you could suffer cable break, or general power failure that you cannot resolve quickly - so the most important thing to establish is "where am i" ... the next is "where am i going? and is it safe to do so?" ...