According to wiki: “The Mercator projection was designed for use in marine navigation because of its unique property of representing any course of constant bearing as a straight segment. Such a course, known as a rhumb (or, mathematically, a loxodrome) is preferred in marine navigation because ships can sail in a constant compass direction, reducing the difficult, error-prone course corrections that otherwise would be needed frequently when sailing a different course.”
But also according to wiki: “A rhumb line can be contrasted with a great circle, which is the path of shortest distance between two points on the surface of a sphere. On a great circle, the bearing to the destination point does not remain constant. If one were to drive a car along a great circle one would hold the steering wheel fixed, but to follow a rhumb line one would have to turn the wheel, turning it more sharply as the poles are approached. In other words, a great circle is locally “straight” with zero geodesic curvature, whereas a rhumb line has non-zero geodesic curvature.”
Isn’t this contradictory? Maybe I’m not getting what constant bearing means. But why would sailors prefer to continue turning in a direction, as opposed to going constantly straight for the duration of the trip? Doesn’t it make more sense to do the latter
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Trying to keep it simple, so experts plz don’t nitpick
On a great circle route, your heading (I’ll neglect heading vs course and magnetic variation and stuff to keep this simple) is constantly changing over the route. Computers make this easy, as they’re constantly calculating. It’s harder to calculate (and execute) by hand.
A rhumb line is much simpler. Sail this heading, and keep sailing it. You can break it up into a series of rhumb lines if you want. Down near the equator, the difference between great circle and rhumb line distances is minimal…often on the order of a few percent or less…and that’s where they did a whole lot of sailing back in the early days. The differences really only start to become significant (and can become quite significant) when higher latitudes are involved.
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