Getting from point A to point B can be a problem if you're in new territory or crossing a great watery expanse. It helps to have a map or chart.
If you do have a chart, like one at
Open Sea Map, you can use
dead reckoning to get where you want to go. According to Wikipedia, this method is subject to a build-up of errors, but generally it begins with
...a known position, or fix, which is then advanced, mathematically or directly on the chart, by means of recorded heading, speed, and time.
Celestial navigation looks to the stars, Sun, or Moon for directions.
Celestial navigation, also known as astronavigation, is a
position fixing technique that has evolved over several thousand years
to help sailors cross oceans without having to rely on estimated
calculations, or dead reckoning, to know their position. Celestial navigation
uses "sights," or angular measurements taken between a celestial body
(the sun, the moon, a planet or a star) and the visible horizon. The sun
is most commonly used, but navigators can also use the moon, a planet
or one of 57 navigational stars whose coordinates are tabulated in the Nautical Almanac and Air Almanacs.
***
 |
| This classic star
trail image shows how stars move in our sky as Earth rotates. More than
150 individual one-minute digital images were stacked in Photoshop. A
first-quarter moon illuminated the surrounding landscape for the
duration of the exposures. credit: Peter Michaud, Gemini Observatory, Space.com |
***
You can download
free nautical almanacs in PDF form at
NavSoft; there's a free version of AstroNav available, too.
On your way to the open ocean, you'll have to avoid running into a sandbar or rock. Topographical nautical charts plot underwater features along the coastline.
NOAA offers such charts, as do a number of businesses.
Sextants are used to fix position and can be used to navigate, sound (for hydrographic surveying), and survey on land. More information about sextants can be found under
reflecting instrument.
***
***
For a good article that may help ordinary folk who are out at night and just want to find their way home, take a look at "
How to Navigate by the Stars," published on Mental Floss. Here's a sample:
Forgot to memorize your constellations? There’s an easy fix. Simply
place two sticks in the ground and set them one yard apart. Now pick a
star—any star. Line it up with the tops of both sticks, as if you were
looking down a rifle sight. The earth’s rotation will make the star
“move.” If it runs left, you’re facing north. If it shifts right, you’re
south. If it rises, you’re east. If it sinks, west.
Oh, and by the way, Space.com reports a total lunar eclipse tonight:
This first total lunar eclipse of 2014
is set to begin tonight (April 14) into the wee hours of Tuesday
morning (April 15). The lunar eclipse is set to begin at about 2 a.m.
EDT (0600 GMT), and it should last about 3.5 hours. The eclipse should
be visible, weather permitting, through most of North America and part
of South America.
-- Marge
