Coastal Navigation Before GPS

Before satellite navigation, sailors relied on a combination of dead reckoning, celestial observation, and coastal landmarks to determine their position at sea. Lighthouses, buoys, and charted headlands formed a network of visual reference points that experienced navigators used to cross-check their calculations.

Dead reckoning involved estimating a ship's current position based on a previously known position, along with recorded speed, heading, and elapsed time. Small errors could compound over a long voyage, which is why navigators regularly corrected their estimates using visible landmarks or star sightings whenever possible.

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Celestial navigation used the position of the sun, moon, and stars relative to the horizon, measured with instruments like the sextant, to calculate latitude and, with an accurate clock, longitude as well. This method remained a critical backup for ships well into the 20th century, even after early radio navigation aids became available.