The Symmiktos Method: A Robust and Accurate Estimation Method for Acoustic Doppler Current Estimation

Document type: Conference Papers
Peer reviewed: Yes
Author(s): Thomas L Lagö, Per Eriksson, Mikael Åsman
Title: The Symmiktos Method: A Robust and Accurate Estimation Method for Acoustic Doppler Current Estimation
Conference name: Oceans '93 : proceedings, [October 18-21, 1993, Victoria, BC, Canada] : engineering in harmony with the ocean
Year: 1993
Pagination: 381-386
ISBN: 0-7803-1385-2 (hft.) 0-7803-1386-0 (inb.) 0-7803-1387-9 (mikrofiche)
Publisher: IEEE
City: New York
ISI number: A1993BC53C00071
Organization: Blekinge Institute of Technology
Department: Dept. of Signal Processing (Institutionen för signalbehandling)
Dept. of Signal Processing S-372 25 Ronneby
+46 455 780 00
http://www.hk-r.se/isb/isb_en.html
Authors e-mail: Thomas.Lago@isb.hk-r.se
Language: English
Abstract: Sea current measurements have been of great interest for many years. Mechanical current instruments are still widely used for such applications. Electronic devices, using ultrasound, can measure the current at different depths. The current at different depths, or cells, is directly proportional to the doppler shift in that cell. When the burst or ping is transmitted toward the surface, scattering occurs from entrained air bubbles and other particles in the water. This is the base for the doppler signal and the measurement principle for an acoustic doppler current meter. Due to the variance in the scattering signal, a trade-off between burst length, cell size and measurement time has to be made. Bias in the doppler estimate is often a drawback when trying to decrease the variance. Traditional estimators are based on a Gaussian assumption about the scattered signals distribution, or rather the doppler shift distribution. A robust and accurate estimate of the doppler shift consists of a bias-free estimation of the current with a low variance for various types of data. The Symmiktos method is an estimation method that has improved the accuracy of the doppler calculation, compared to standard methods. This paper contains a description of the background to acoustic doppler current meters, the scattering signal, the traditional assumptions for a doppler estimate, as well as suggestions for the improvement of models for the estimation. An introduction to the Symmiktos method, and the models that are the foundation for this new estimation method is also presented.
Subject: Signal Processing\Hydro-Acoustics
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