The method and measurement system to measure the water level of a water body

A method for measuring the water level of a body of water by means of a reflector (1, 101, 201, 301, 401, 501) having a number of reflecting surfaces (1a, 1b) for the reflection of electromagnetic radiation in a predetermined wavelength range, and in or on the waters is provided so that through the water surface (W) of the water and one or more reflecting surfaces (1a, 1b) of the reflector (1, 101, 201, 301, 401, 501) a corner reflector is formed, - electromagnetic radiation in the predetermined wavelength range which is emitted from a located above the body of water jet means (3), in such a way to the reflector (1, 101, 201, 301, 401, 501) is incident on the incident radiation at the corner reflector based a multiple reflection involving the water surface (W) is reflected back; - over the life of the transmitted and back-reflected radiation, the distance between the beam means (3) and reflecting center of the corner reflector is measured and from this the water level (W) of the water is determined, in the determination of the water level of the water (W) a three-dimensional position of the jet device (3) and a two-dimensional, the position of the reflector (1) be considered in top view of the earth's surface descriptive position.