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Fig. 4. Dewowing of vertical radar profiling (VRP) data from Trecate. The upper row of figures refers to data from 1.5 m b.g.l.; the lower row refers to 8.5 m b.g.l. Plots (a) and (e) are raw field data. (b) and (f) are the corresponding dewowed data using a residual median filter with length equal to 80 ns. (c) and (g) are dewowed data using a residual mean filter with length equal to 80 ns. (d) and (h) are dewowed data using a residual mean filter with length equal to 10 ns. The detrimental effect of the "wow" is more serious at depth, requiring that dewowing is applied (note that the "wow" in (e) makes first break picking impossible). The only dewowing algorithm that worked properly for all depths was the residual median filter (b) and (f). Spurious precursors were introduced by the residual mean filters.
