The Development of Radar and Sonar
Overview
Although they rely on two fundamentally different types of wave transmission, Radio Detection And Ranging (RADAR) and Sound Navigation and Ranging (SONAR) both are remote sensing systems with important military, scientific, and commercial applications. RADAR sends out electromagnetic waves, while active SONAR transmits acoustic (i.e., sound) waves. In both systems these waves return echoes from certain features or targets that allow the determination of important properties and attributes of the target (i.e., shape, size, speed, distance, etc.). Because electromagnetic waves are strongly attenuated (diminished) in water, RADAR signals are mostly used for ground or atmospheric observations. Because SONAR signals easily penetrate water, they are ideal for navigation and measurement under water.
Background
For hundreds of years, non-mechanical underwater listening devices (listening tubes) had been used to detect sound in water. As early as 1882, the Swiss physicist Daviel Colladen attempted to calculate the speed of sound in the known depths of Lake Geneva.
Based upon the physics of sound transmission articulated by nineteenth-century English physicist Lord Rayleigh (1842-1914) and the piezoelectric effect discovered by French scientist Pierre Curie (1509-1906) in 1915, French physicist Paul Langevin (1872-1946) invented the first system designed to utilize sound waves and acoustical echoes in an underwater detection device.
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