Performance of an acoustic Doppler current estimation method based on the Symmiktos method

The estimation of water current by using acoustic Doppler current meters is a well-known method. Determination of the water current is based on the Doppler shift caused by the movement of small particles in the water, and related to the current as an average. These movements cause a Doppler shift with an assumed Gaussian-shaped distribution in time. Due to scattering from many different bubble sizes and other scatterers, a complex Doppler signal is received with a large variance. The Symmiktos method estimates the first moment of the Doppler signal by using a frequency domain method. This method combines linear and nonlinear digital signal processing. The result is a robust and accurate estimation method with a very low bias. In order to verify this performance, a mathematical model of the Doppler shift is used, where effects from different bubble sizes and other reflexes can be taken into account. This mixed statistical model is then used for synthesizing data with different levels of complexity, but with known parameters. These synthesized data makes it possible to quantify the accuracy and performance of different estimation methods such as the Symmiktos method or the covariance method.