3D (Areal) Filtering
Notch Filter
The combination of an S-filter and an L-Filter may be used to eliminate a bandwidth of spatial wavelengths from analysis, maintaining the spatial structure with wavelengths less than the S-Filter Cutoff and spatial wavelengths greater than the L-filter Cutoff.
When the spatial wavelengths of the structure to be analyzed consists of spatial structure finer spaced that the S_Filter Cutoff and spatial structure with coarser spaced features than the L-Filter cutoff, the filter is referred to as a Notch Filter.
The figure below demonstrates that with a Notch Filter, features such as the isolated wider peaked regions (circled in the images) and moderate spatial structure lengths between the dominant mountain/valley features are eliminated.
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As measured surface without filtering consisting of finer spaced features superimposed on longer wavelength components. |
Notch Filter applied, resulting in the longer spatial wavelengths and shorter spatial wavelengths being preserved for subsequent analysis. |