Cover Design by Gabriel Romeu

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Learn the basics of navigation with this 128 page book. Originally a series in ANorAK magazine, it has been expanded and produced as a book due to the many positive comments received and encourgement from many people.

Navigation is the process of knowing where you are at any given time when traveling from point A to point B. To do this effectively you will need to know how to read a chart, how to use your compass, estimate speed and predict currents. Every navigation decision depends on knowing where you are at that moment.

There are two types of navigation, dead reckoning and piloting. Piloting is using known landmarks and references to locate your position. If you are paddling next to a lighthouse you can look at the chart and know exactly where you are. If you are further away it is not as easy. If you have only one distant landmark then you need to take a compass bearing to it and approximate the distance. Two distant landmarks require that you take a bearing to each and your location is the intersection of the lines.

Dead reckoning is an educated estimate of your present position compared to where you were a while ago in the absence of suitable landmarks. To do this with any reasonable degree of accuracy, you need to know your approximate speed, the direction you are going and how much the wind and currents are altering your course. The work ‘dead’ most likely evolved from ‘ded’ an abbreviation for deduced.

While we are at it lets also define the three fundamental names given to directions. A Heading is the direction the kayak is pointed. A Course is the direction you want to go and a Bearing is the direction to a landmark. They don’t always coincide. You may be paddling a compass course of 90 degrees but your heading may need to be at 75 degrees to compensate for a current. This may even fluctuate between 70 and 80 due to wave action or wind but your bearing to a landmark may remain at 120 degrees

CHARTS AND MAPS

A nautical chart is a scaled representation of an area of the earth’s surface. It differs from a map in that it shows details such as water depths, tidal ranges, shoreline composition, buoys, lights, and other things of interest to mariners. To explain all the symbols used on charts, there is a small booklet available simply called "Chart No. 1". A nautical chart will also depict a compass rose to show true North and magnetic North. This difference is called a variation and is noted on the rose along with whether it is East or West of true North. You must remember to allow for this when going from chart to compass or compass to chart. Also on the rose is a yearly increase or decrease, which can be ignored. It is usually only a couple of minutes of change per year and by the time it changes a degree or two to make a difference in navigation, the chart will long be outdated.

The scale of a chart is important to a kayaker. With a small-scale chart many things we need to know will be omitted for clarity. The location of underwater rocks for instance will not be shown. Shoreline configuration will be less accurate. A 1:40,000 scale is about the smallest chart to be useful for reading shoreline features. If a 1:20,000 scale chart of the area is available it would be more meaningful for our use. It would show the smaller coves more clearly where we might possibly take shelter. Also the shoreline composition may be shown telling us whether or not it is sand, rock or a mud beach. Remember though, with a 1:20,000 chart, the area covered will only be about 10 miles across. Using these scale charts on an expedition would make a large stack of paper to carry around. If a long trip is planned, then a small-scale chart is better for planning the overall route. Use judgment when choosing a chart.

These are imaginary lines used to form a grid around the globe. They are expressed in degrees, minutes and seconds since they are angular measurements of a circle. Latitude lines are perpendicular to the earth’s polar axis (parallel to the equator) and longitude lines are ones that circle the globe passing through the North and South poles (vertical).

Longitude lines are also called meridians. Most nations use the one passing through Greenwich, England as their prime meridian. On the opposite side of this at 180 degrees is the International Dateline where the day begins. Latitude lines are recorded as either north or south (of the equator) and longitude lines are either east or west (of the Prime Meridian)

To use these invisible grid lines, we need to break it down further than degrees. This we do by using Minutes and Seconds. All circles consist of 360 degrees. Each degree is divided into 60 minutes and there are 60 seconds to a minute. Remember, each degree at the earth’s surface is equal to almost 70 statute miles, each minute equal to 1.15 statute miles and each second is equal to 33.82 yards or a little more than 100 feet. This is why we use all three to identify our position. Now for something really useful. One nautical mile equals 1 minute of latitude anywhere on the earth’s surface. This is not coincidence! This is how they defined a nautical mile. Latitude lines are parallel to one another so this is possible, but since longitudinal lines converg at the poles, one minute of longitude equals 1 nautical mile only at the equator. You can see now how a chart can help you determine how far you have gone by using the latitude lines as a distance scale.

It is important to distinguish between these two terms. Tides are the result of the moon’s gravity pulling the water toward it into a bulge (high tide). As this happens, the waters on the sides of the earth get shallower (low tides). At the opposite end of where the moon is, another bulge forms due to centrifugal force. Tides are a vertical motion. If you have water rising and falling at the coast, then at some point this water will move in and out of the land’s contours. This horizontal motion is called a tidal current and opposed to a river current, it reverses its direction. When it flows into an estuary it is a flood current and as it goes out it is called an ebb current. When the moon, earth and sun are in alignment (you know this as a full moon and a new moon), it is called a Spring Tide and the gravity of the two forces join together and create a stronger pull resulting in a higher tide.

 Neap tides are lower than normal and occur when the moon is at a 90-degree angle to the earth and sun (first quarter and last quarter). In addition to this, the moon is in an elliptical orbit around the earth. When the moon is at the far end of the orbit (apogee), tides are lower still. When the moon is close to the earth (perigee) tides are much higher than normal.

  The actual bulge height in Open Ocean is only about 18 inches. This bulge follows the moon around and it builds in height as it moves just as a wave does when it reaches shallower water. As it approaches land where the sea floor starts to rise or the land gets constricted, the height of the tide increases. In some areas such as in the Bay of Fundy or the northern part of the Sea of Cortez tides can reach heights of 40 feet.

The relationship between tide height and the tidal current is not always as you would guess. It sounds reasonable to assume that when the tide stops going up or down, it should be slack water. This simplified reasoning is frequently wrong. It is possible for the tide to be rising and the current ebbing. This thinking can get a kayaker into serious trouble especially if it is a strong current.

A good approximation of the rate of rise or fall of tides is the Rule of Twelfths. Let’s say you have a tidal range of 6 feet in your area. We round off the time difference between high and low tide of 6 hours and 15 minutes to 6 hours. Tide range of 6 ft divided by 12 equal .5 ft.

As you can see by the chart above, the water rises or falls slower in the 1^st and last hours and it would rise or fall the fastest in the middle two hours of the tide change.

Compasses commonly used in kayak navigation are the marine compass and the hikers compass. There are important distinctions between them. Hiking compasses have the numerical scale attached to the housing and must be rotated into alignment with the needle before it can be read. A marine compass has the scale attached to the needle and as the boat turns the numbers on the compass remain stationary relative to the earth and the housing with its imprinted index turns. Marine deck type compasses are also usually larger and may be well damped so they do not swing as much with each passing wave and are designed to tilt more without sticking. These are predominantly used for steering purposes.

Hand held compasses indeed have their own advantages. It is much easier to take a bearing to a landmark by aiming a hiker’s compass without turning the kayak around to face the object. You can take bearings off of charts when plotting your course. For land use, many have adjustments to offset the index to compensate for magnetic variation. This is not important when using nautical charts since the compass rose has an offset scale.

One important item to remember is to avoid placing metal objects under the deck when packing. This will cause false readings.

 TO GET COMPASS READING OFF CHART. (Using hikers compass)

1. Align edge of hand held compass from starting point to destination.

2. Rotate bezel so that North is correct and lines on compass are parallel with longitude lines.

3. Read bearing from bearing arrow. (This is true North)

4. Adjust for magnetic variation. Plus on West (POW).

TO TAKE A COMPASS BEARING. (Hikers compass)

1. Look at desired object with bearing arrow on compass.

2. Align North

3. Read bearing. This is magnetic North.

If plotting on chart, remember to subtract the variation first.