Originally Posted by Jdege
There was one of the Delos videos where they were threading their way through some shoals along a tidal river when their GPS/Nav went out.
This is Exactly why one keeps a running DR, on Paper Charts, all of the time. Otherwise they're simply excess baggage.
It's nice to be think you can rely on paper charts and sextants as a backup, but if you've been relying on the electronics, and they suddenly go out, while you're in a tight spot where you don't have sea-room, how long will it take you to dig out the paper charts and identify your position?
Assuming that for whatever (foolish) reason you haven't been keeping a proper DR plot, & this happens. Then the proper course of action (if possible), is to hold your position. Via either anchoring, & or by shooting bearings to prominent topographical features, using your echo sounder, etc.
Until you pull out your paper charts, get your head extracted from your backsided, & fix your position. So that you can then carry on with making way... While maintaining a Proper DR plot, whilst doing so.
To maintain a proper DR, you plot your position (with course & speed info) every;
- Hour on the Hour
- Every Course Change
- Every Speed Change
- And of course, for every; Fix, Running Fix, Sun Line, Line of Bearing, etc., etc.
Plus, basically for any & every time that you acquire a piece of navigational data which helps you to establish where you are, or can be used in conjunction with another piece of nav data, in order to do so.
BTW: Most, if not all, of the above is stuff which gets entered into the ship's log by the designated watch keeper anyway. Along with a number of other things. At regular intervals; usually the ones delineated above.
Though here's a question, which is Key
to all of this/answering your question.
Why rely entirely on electronics, & electronic charts, completely, to begin with? <--
Is it not simply prudent to use a variety of types of navigational tools, & formats, in order to keep track of your position?
To me, it makes sense to make up a "cheat sheet" of all of the key points, nav wise, for a new area. Both; on a sheet of paper, & on the chart(s). As compiled from the pertinent nav references
So that what I have is a "briefing sheet" for the new area, which covers all of the key points, in an easy to read at a glance format. Thus, if/when the fecal material hits the fan, I'm already prepared nav wise.
(PS: Said briefing sheet can be pasted into either; the Ship's Log Book, or a Nav Reference Book. So that if you're operating in that area a little while down the road, then you have the basics to work from/with already - though in need of updating).
Making up such an info/data sheet, is (a longer, nav type version of) kind of like plotting escape bearings, as well as danger
bearings, once I'm bedded down in a new anchorage. So that if I have to leave in a hurry, & visibility is poor to non-existant, I simply follow my pre-planned route
All of the info's right there. So that I can concentrate on the 101 other crazy things which will undoubtedly pop up in said scenarios.