Hyperbolic navigation systems can be divided into two main classes, those that calculate the time difference between two radio pulses, and those that compare the phase difference between two continuous signals.
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One of the last hyperbolic navigation systems to enter operational use was one of the earliest to be developed; Omega traces its history to work by John Alvin Pierce in the 1940s, working on the same basic idea as the Decca phase-comparison system.
