N is for Navigation

 

a  to z - nautical chart

Navigation is the art/science of moving from one place to another whether you’re on a boat, on foot or even on the stormy seas of the internet. It may sound really simplistic to say, but there are two things one needs to know for effective navigation. The first thing to know is your present location, where you are. The second thing to know is your desired location, where you want to go. That is the case for all navigation, not just nautical navigation. After you know those two things then you go about determining how you get there. On land you look at a map to tell you which road to take, determine how long it will take you to get there given the vagaries of traffic, etc. In these modern times a GPS will direct you down which road to take, but don’t depend on GPS too much. Once in Switzerland I went exactly where the GPS told me to go and for some strange reason it took me on the most roundabout route imaginable. Maps, charts and forethought still have their place.

At sea it’s a little more complex. The simplest way is with Global Positioning System, or GPS. With GPS you look at the screen, see where you are, punch in the numbers of where you have to go and it gives you a direction to go. Of course when you set your course you have to take into account leeway (the amount of movement sideways due to wind), water currents that may shift you sideways, make you go faster or slower depending on conditions and wave action that throws you around. Besides there’s the old quote from a guy I heard from Maine, ‘she ain’t a-goin’ where she’s a-pointin’’ … which means that under sail the boat is always slewing a little sideways so you have to take that into account.

There is coastal navigation and at-sea navigation. Coastal Nav is done by looking at the chart of the area where you are sailing, taking cross bearings on objects that you can see and plotting those bearings on the chart to determine where you are.

a to z - lines of postion

This is called taking a fix. Theoretically it only takes two bearings to take a fix, but three is a really good idea. That way the intersection of the three lines forms a tiny triangle and you assume that you’re somewhere in that tiny triangle.

Celestial Navigation is a bit more complicated, but it’s basically the same thing, except rather than bearings on objects you can see, you establish lines of position based on celestial objects you can observe with a sextant. A sextant, by the way, is just an instrument that measures the angular position of the object above the horizon. Simple. Your handy dandy nautical almanac is the book that tells you where celestial objects are at any time (a very accurate time) within the year of publication and reduction tables (big books loaded with tables of numbers) along with the navigation forms to guide you through the arithmetic, help you establish your lines of position. If you’re really interested in learning celestial nav, there are many books out there that will take you through the details. But as the circumnavigator Eric Hiscock said: “Setting the course, keeping the dead reckoning up to date and fixing the position by observations of the celestial bodies, call for nothing more than simple arithmetic, a little geometry and some dexterity in handling the sextant.” He left out that close attention to the time is crucial. For instance if you draw a line from the center of the sun to the center of the earth, the intersection where that line intersects the surface of the earth moves about 4 miles every second. Which is pretty fast when you’re taking a sun sight, trying to navigate your way from the open ocean to an island just a couple of miles wide. But still, it doesn’t take a rocket scientist to do it, just someone who can do some simple arithmetic and takes care in reading the sextant and taking the time.

a to z - taking a sextant sight

So despite all the mysterious talk, it’s really not all that hard.

Isn’t that cool?

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3 thoughts on “N is for Navigation

  1. I want to go sailing! Somewhere in pretty weather with the wind blowing through my hair. Did I tell you that I’m a “professional ballast”? I didn’t know what it was until the first time I went sailing with some guys and they told me I could be the ballast.

    • That sounds pretty mean to me, though when I went sailing with some guys that raced, their term for people who were new to the boat was ‘rail meat’, i.e. ‘sit up there and be ballast so the rest of us can have fun.’ … some people have no sensitivity atall …. xx

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