Have I missed something ? - having batteries, back up and redundancy does not do much good should the GPS sats. be taken down.
Was not that the point of the post as well ?
I remember accidentally cutting thru my antenna cable one season ... the chartplotter was bl..dy useless, although I did manage to use the chart by scrolling the cursor in keeping with my (supposed) route to pick out shoals and upcoming nav. points, etc. - but it was nigh on impossible
Next day I went out and got a set of charts
Like when the TV is on the blink ... I always have a book to read ;-))