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. 2022 Jan 20;22(3):791. doi: 10.3390/s22030791

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© 2022 by the author.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Countour map plots (a,d,g,j,m), PSDs (b,e,h,k,n) and texture direction (c,f,i,l,o) graphs of the HFNS defined by the: Gaussian (a–c), robust Gaussian (d–f), median (g–i), spline (j–l) and FFTF (m–o) filter, cut-off = 0.015 mm.

Countour map plots (a,d,g,j,m), PSDs (b,e,h,k,n) and texture direction (c,f,i,l,o) graphs of the HFNS defined by the: Gaussian (a–c), robust Gaussian (d–f), median (g–i), spline (j–l) and FFTF (m–o) filter, cut-off = 0.015 mm.