| CPC G01B 15/02 (2013.01) [G01S 13/931 (2013.01)] | 20 Claims |

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1. A method comprising:
transmitting, at a transmitter element of a detection device, a wave signal that is reflected by a target above a reflecting surface;
receiving, at each of two receiver elements of the detection device that are vertically aligned with one another, the wave signal reflected by the target, the wave signal propagating via multiple paths caused by the reflecting surface;
while a target distance between the detection device and the target varies over time, measuring a phase difference between the reflected wave signals received by the two receiver elements;
determining, from the measured phase difference, a physical quantity fluctuation in relation to the target distance; and
deriving information on a height of the target from the physical quantity fluctuation.
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