Every newly commissioned ship in the U.S. Navy's surface fleet carries a copy of Nathaniel Bowditch's "The American Practical Navigator" (1802) on its bridge. This thick encyclopedia on maritime navigation is packed with data on the latitudes and longitudes of various landmarks -- from the Bugio Lighthouse in Lisbon, Portugal, to the Kannonzaki Lighthouse in Yokosuka, Japan.
It also provides detailed instructions on how to use a sextant to measure a ship's current location by observing the sun, moon, stars and horizon. Though the act of carrying the book on every ship was largely ceremonial, the threat of China's electronic warfare has increased the likelihood that the ship's quartermaster will reach for the Bowditch.
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