If we are on a long passage, we record our position every 30 to 60 minutes, confirm it visually if possible and also record compass heading and speed. This way, if we lose the electronics, we are able to estimate our position. I will also check that depth on the sounder is reasonable for where the gps says we are. If we are close enough to pass a nav aid or very notable land feature, we use removable post it notes to mark it and the time on a chart. Pretty simple back up.
So do we. The only thing I add is:
I draw a vector to the destination on a paper map. I then plot the dot (time, incl GPS coord for LAT and LON) every 30-60 minutes depending on the weather. Ii will actually go two hours or more for long runs in the daylight where the weather is good.
My log has:
Time (military), coord, wind (T), speed (I only use SOG), heading (Mag... that is just me), and sea state. I also put in under a log anything unusual or any changes made. I make my own logs and keep them in those lab looking books that are ral cheap and cannot have paper torn out.
Also, put in where you are going from and where to. Mark completion. It is not that you will forget on the trip, but when makin return trips it is a awesome tool (we used it a LOT) to plan your departure. Believe me, you will forget how long it takes to get from Tampa to FMB or Marathon to Tortugas, whatever... and this is real time. It is important in most of these areas where we go not to make arrival at night, and in some cases (like he Tortugas) I MUCH prefer arriving around noon when we can see Coral heads well.
Just some thoughts.
ALso David, to answer you question, it is good to know because 1) Electronics will fail. 2) THe pure aspect of seamanship.
Great job reaching that stuff. Now what is a compass again and which button on my chartplotter do I press to get it?? (snicker).