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Tools commonly used for navigation include:
- Charts (of course). They are essential since they give you a visual orientation and features regarding the body of water you wish to sail. Charts are now available online and are included as software in many navigation instruments.
- Dividers. This is a handy tool for measuring distances on a chart.
- Magnifying devices for reading small print, especially in subdued light.
- Compass. In spite of GPS, the compass is still a major navigational tool.
- Parallel rulers are used for moving lines on charts.
- Drawing triangles.
- Course protractor (Breton plotter is one example).
No matter the chart in use, the navigator’s work largely involves the determination of direction and distances. The most useful tools for actual chart work are:
The parallel ruler is used to draw lines of position and measure directions. The rulers are able to “walk” a line from one place on the chart to another keeping the ending line parallel to the first. Below, the problem has you transferring drawn latitude and longitude lines at specific intervals to exact latitude and longitude position lines. Then it compares a plotted direction against the compass rose to gain a compass direction.
Press the play button.
Parallel Ruler Animation
Note that the compass rose is marked so that the inner dial shows magnetic while the outer dial shows true. Since you measured 37 deg T on the chart on the compass rose on the outer dial, this is shown on the inner compass rose dial as 51 deg M. Thus using a compass you’d see Bartlett Reef ATON at 51 deg.
Parallel rulers are also used to place a known location on the chart. Given a lat/long position from a GPS, the rulers can transmit the latitude from the vertical edge of the chart, and the longitude from the horizontal edge.
The disadvantage of parallel rulers is that it is difficult while a boat is moving to hold the rulers tight against the chart while trying to “walk” the lines to the compass rose.
Above, we used the dividers to measure the distance from the plotted position to the Bartlett Reef on the chart. We transferred the dividers to the latitude scale on the right (or left) side of the chart. One point is against 15′ the other 16.5′. Thus the distance is 1.5 nm.
The Breton Plotter
The Breton plotter tends to be more widely used than the parallel rulers. Below we have added an animation of using the Breton plotter to determine a course in Long Island Sound from a buoy we are passing close to— to the entrance buoy to New London Harbor. We want to know the true and magnetic course. Note this is not equivalent to your heading. Heading will take into account leeway and current.
Bretton Plotter Animation
The Nautical Slide Rule
The nautical slide rule is one of the handiest and simplest devices to have around. If you have two of the three variables of speed, distance, and time, it will calculate the other.
- If you know speed and distance it will calculate time.
- If you know distance and time it will calculate speed.
- If you know speed and time it will calculate distance.
Just spin the dials to align with the marks and read the remaining dial.
Below is a video in which you can see how the slide rule calculates the distance traveled by a boat traveling at 7 knots for 3 hours.
Nautical Slide Rule
Keep pencil leads very sharp for pinpointing positions. Sharpening with a sailing knife is not the way to go!
The hand-bearing compass (HBC) is fundamental and used in measuring bearings of charted objects from a ship’s deck.
A sounding, the water depth, is another important element in coastal navigation. Soundings are usually determined by the ship’s depth sounder. In case of instrument or electrical failure, it is wise to have a lead line on board to find the water’s depth in those situations. A lead line is a length of line with a weight attached to one end. The weight is dropped into the water and allowed to reach the bottom. Depth is determined by reading a pre-colored scale on the line.
Binoculars are invaluable for sighting objects on shore or in the water to be used as navigational aids. They are of course essential in our efforts to monitor other traffic as well.
Whenever a vessel is maneuvered during limited visibility, a spotlight can become essential gear to locate navigation aids.
Night Vision Goggles
For less the a few hundred dollars, you can pick up a set of night vision goggles that will definitely assist your safety operations at night.
You can learn more in the Skipper Course....
Knowledge and theory for longer distances and overnight sailing in diverse conditions. The Skipper Course is a comprehensive sailing course for beginner to intermediate sailors wanting to learn how to sail larger sailboats 26ft to 56ft. Or upgrade to the Skipper Course Bundle to also master maneuvering under power and docking!