Join Date: Nov 2008
Location: Penobscot Bay, Maine
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Re: Variation question for chart navigators
My perspective, FWIW, is a little different. It's true that the amount of change in variation won't matter much given the various limits on precision cited above. (Although the more times you use a slightly inaccurate course, the more significant the inaccuracy can become). But to me, there are reasons why it makes sense to figure the change in, always.
First, it's very easy--multiply the annual change by the age of the chart and add/subtract it to the variation number. It becomes second nature.
Second, doing automatically it is easier than making a conscious decision, in every instance, whether to do it or not. Like many other aspects to managing a boat, having standard procedures has many advantages. Not least of which, it makes sailing more relaxing when you have fewer judgment calls to make, and potentially fewer mistakes. And there's satisfaction in knowing a 'right' way to do things like navigation (and your own right way can differ from mine), and getting good at doing them that way.
Another reason: it makes you look at the age of your chart, which is obviously important for other reasons, and you might not otherwise.