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Wednesday, November 15, 2017

Navy Submarine RADAR History, Earth Curvature

In 'History of Airborne and Shipboard Periscope Detection Radar Design and Developments' we see the following in a discussion about radar horizon:
Not surprisingly, the radius of the earth enters into calculations of the geometrical range to the horizon; calculations of the range to the radar horizon account for refraction by assuming that the radius of the earth is 4/3 as great as its actual value. For sensor altitudes small in comparison with the radius of the earth, the distance to the radar horizon in nautical miles is 1.23 times the square root of the altitude in feet. Thus, for a typical airborne PDR altitude of 500 feet, the range to the radar horizon is 27.5 nmi, and for a nominal mast-mounted shipboard antenna height of 70 ft, it is about 10 nmi. Note that common surveillance radar heights for a U.S. cruiser or destroyer are 100-120 ft, and, for an aircraft carrier, 150-180 ft.
Just another nail in the coffin of claims that nobody ever takes curvature of the Earth into account.

Pretty much every book on RADAR discusses both the effect of Earth curvature and refraction on RADAR.

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