Comparison of Different Bin-mapping Methods for a Bottom-mounted Acoustic Profiler

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  • 1 Department of Geophysics, University of Helsinki, Helsinki, Finland
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Abstract

Acouste Doppler current profilers (ADCPS) can measure profiles of velocity components and some other properties of bodies of water. If the profiler is firmly mounted, the profiles can be recorded without immediate coordinate transform. This gives more flexibility to the instrument settings and increases the capabilities of the instrument. If the instrument tilts, some data cell positioning—bin mapping—is usually needed in the post-processing of the data. The errors during that procedure depend on the degree of the tilt and the method used. If there are high gradients in the profiles, maximum errors can easily be greater than the statistical accuracy of the ADCP, If the tilts are fixed, these errors occur systematically at equal distances. In this study it is shown that the errors can be made smaller by slicing the beam profiles or by taking weighted averages instead of straight nearest bin selections. The disadvantage of these methods is that all sharp changes will be smoothed.

Abstract

Acouste Doppler current profilers (ADCPS) can measure profiles of velocity components and some other properties of bodies of water. If the profiler is firmly mounted, the profiles can be recorded without immediate coordinate transform. This gives more flexibility to the instrument settings and increases the capabilities of the instrument. If the instrument tilts, some data cell positioning—bin mapping—is usually needed in the post-processing of the data. The errors during that procedure depend on the degree of the tilt and the method used. If there are high gradients in the profiles, maximum errors can easily be greater than the statistical accuracy of the ADCP, If the tilts are fixed, these errors occur systematically at equal distances. In this study it is shown that the errors can be made smaller by slicing the beam profiles or by taking weighted averages instead of straight nearest bin selections. The disadvantage of these methods is that all sharp changes will be smoothed.

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