grid_filter_5

Filter Clumps

Author(s) Module: Victor Olaya, (c) 2004

Author(s) Wiki Documentation: Vern Cimmery, (c) 2011 2011 (kapcimmery at hotmail dot com)

License Wiki Documentation: Creative Commons Attribution-ShareAlike 3.0 Unported License

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Description:

The Filter Clumps module is used to identify groupings of grid cells having the same data value. The minimum size for a group is specified by the entry for the ‘Min. Size’ option.

Input
Grid system
The entry for the ‘Grid system’ parameter must be the grid system the input grid data layer is a part. In order to be chosen, the grid system must be loaded in the current work session.

>>Input Grid
The grid data layer containing cells with the same cell values that will be identified as "groups" or "clumps".

Output
<<Filtered Grid
The output for the module is identified in the value field to the right of the ‘<<Filtered Grid’ parameter. The default is “[create]”. The default name for the output grid data layer is “Filtered Grid”.

Options
Min. Size
There is a single option in the ‘Options’ section: ‘Min. Size’. The default entry for this parameter is “10”. This would mean that the smallest grouping of grid cells that would be searched for and identified as a clump on the output grid layer would be 10.

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Execution Example:

This example uses a grid data layer depicting slope gradient. The slope for each grid cell is portrayed by an integer value representing degress, 1 through 90. The default entry for the 'Min. Size' parameter is "10" and will be used to define the minimum clump of cells. In this case the cell size is 90 square feet. This means that the smallest clump of cells will be for an area 900 square feet in size.

1. Execute the Filter Clumps module.
2. Select the grid system the input grid data layer is a part for the 'Grid system' paramter.
3. Select the 'MCslopeINT' grid data layer from the drop-down list of data layers for the '>>Input Grid' parameter. 'MCslopeINT' is the slope map with slope values as integer values.
4. Verify that the "[create]" option is chosen for the output parameter '<<Filtered Grid'.
6. In the 'Options' section, use the default entry "10" for the 'Min. Size' parameter.
7. When changes have been made to the module parameters and options, click on the 'Okay' button to execute the module.
8. When module execution is complete, the output grid data layer name ('Filtered Grid') will appear in the 'Tab' area of the Workspace.

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Notes: 1. The input grid data layer (for the '>>Input Grid' parameters) must be a member of the chosen grid system.
2. The single output parameter (>>Filtered Grid) must be set to the "[create]" option; "[create]" is the default entry.

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References:

Cimmery, Vern (2011): Filter Clumps, SAGA References, unpublished .pdf document. [PENDING]