Deviation

Section 1.5 Deviation

During a voyage, a navigator uses a reference course which is a line connecting the starting point and the destination, to track their position. If the waʻ a (canoe) encounters winds that push it off its intended course, the navigator can mentally plot their position in relation to the reference course. To prevent missing the destination, navigators must monitor how far they deviate from the intended course. This involves measuring the angle of deviation from the reference course (in units of houses) and calculating the distance traveled.

Trigonometry can be used to calculate the deviation. Figure 1.5.1 shows the deviation when the number of houses and distance traveled while deviating are known. On the other hand, if you have the number of houses but do not know the distance traveled, Figure 1.5.2 offers a method to calculate the deviation using your speed and the time spent while deviating. You can learn more about this technique by studying Right Triangle Trigonometry ¹.

Figure 1.5.1. If you have the number of houses,

h,

and distance,

d,

a canoe has traveled while deviating from its reference course, you can use this tool to calculate the deviation. The unit of measurement for the calculated deviation will be the same units entered for the distance (e.g., nautical miles, kilometers, etc.).

Figure 1.5.2. If the distance traveled is unknown, but you have the number of houses,

h,

the time spent deviating (in hours),

t,

and the speed of the canoe (in knots),

s,

while deviating from its reference course, you can use this tool to calculate the deviation. The deviation will be given in nautical miles.

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