Attack Center: Navigation

Navigation is another requirement that may bring submarines to periscope depth. The U.S. Navy developed the ships inertial navigation system (SINS), which allows a submarine to navigate underwater by keeping track of its relative motion from a known starting point. In practice, errors accumulate, requiring the submarine to approach the surface for periodic updates from external sources at periscope depth.

Until the early 1980s, updates were provided by loran shore stations. Loran is an acronym for long-range radio navigation. Loran has now been replaced by the global positioning system (GPS), a space-based navigational network with ground control and data processing stations. All 24 satellites, the first of which was launched in 1978, are in one of three polar orbits at an altitude of 11,000 miles (18,370 km).

Attack Center on the USS Alabama.

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