Boundary Clean function

Smooths the boundary between zones.

This is a global raster function.

Notes

The function generalizes, or simplifies, rasters by smoothing the boundaries between zones. The function provides options for controlling how the cells of the zones in the input influence the smoothing and the amount of smoothing that will be applied. Each input cell is evaluated using its eight immediate neighbors.

The smoothing process first sorts the neighbor cells by a particular priority. The priority determines which zone from the neighboring cells can replace the value of the processing cell in the output.

The priority can be based on either the value of the zones or the size of the zones. The Sort type parameter determines the sorting type to use.

The default Do not sort setting assesses the priority based on the value of the zones. Cells from zones with larger values will have a higher priority to expand into zones with smaller values.

The size, or total area, of the zones can be used to sort the priority. With the Descending setting, the zones are sorted by size in descending order. The zones with larger total areas will have the priority to expand into zones with smaller areas. With the Ascending setting, the opposite is true: zones with smaller total areas will have the priority to expand into zones with larger total areas.

The amount of smoothing is controlled by the Run expansion and shrinking twice parameter, which determines the number of times the expand and shrinking process will be performed.

With the unchecked setting, the expand and shrink process is performed once. With the checked setting , the expand and shrink process is performed twice, resulting in an additional degree of smoothing of the zone boundaries.

If the values of all eight neighbor cells are the same as the processing cell, the output cell will retain the value of the input cell.

Parameters

Parameter name	Description
Input Raster (Required)	The input raster for which the boundary between zones will be smoothed. It must be of integer type.
Sort type	Specifies the type of sorting to use in the smoothing process. The sorting determines the priority by which cells can expand into their neighbors. The sorting can be done based on zone value or zone size. Do not sort—The priority is determined by zone value. The size of the zones is not considered. Zones with larger values have a higher priority to expand into zones with smaller values in the smoothed output. This is the default. Descending—Zones are sorted in descending order by size. Zones with larger total areas have a higher priority to expand into zones with smaller total areas. This option tends to eliminate or reduce the prevalence of cells from smaller zones in the smoothed output. Ascending—Zones are sorted in ascending order by size. Zones with smaller total areas have a higher priority to expand into zones with larger total areas. This option tends to preserve or increase the prevalence of cells from smaller zones in the smoothed output.
Run expansion and shrinking twice	Specifies the number of times the smoothing process will occur, twice or once. Checked—The expansion and shrinking operation is performed twice. The first time, the operation is performed according to the specified sorting type. Then an additional expansion and shrinking operation is performed with the priority reversed. This is the default. Unchecked—The expansion and shrinking operation is performed once according to the sort type.