Figure 1. Ship-length slide rule of the kind with which the author identified the 860-foot-long battleship Yamato hiding in Hiroshima Bay. On the slider, the horizontal lines from the clock face at left indicate the orientation of the ship on the water, and the family of curves they intersect is labeled by the vertical angle of the ship from the plane's horizon. The appropriate intersection, corresponding to a trigonometric function, is then multiplied by the gunsight target dial setting (in feet) on the bottom fixed scale to give the ship's length, also on the bottom scale.
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© 2001 American Institute of Physics