Focal Statistics

Feature Description

Focal statistics performs statistical analysis on cell values within the neighborhood of each raster cell. It expands a specified range around the target cell and calculates statistical results based on surrounding raster data. Available statistical methods include: Maximum, Minimum, Majority, Minority, etc. Common neighborhood types include: Rectangle, Circle, Annulus, and Sector.

The diagram below illustrates focal statistics, where the value of the cell in the second row and third column is determined by all cell values within its 3*3 rectangular neighborhood.

Figure: Focal Statistics Schematic Diagram
  • Statistical Mode

    SuperMap focal statistics provides 10 statistical modes:

    • Min: Finds the minimum cell value within the neighborhood.
    • Max: Finds the maximum cell value within the neighborhood.
    • Average: Calculates the average value of all cells in the neighborhood.
    • STDEV: Computes the standard deviation of cell values in the neighborhood.
    • Sum: Calculates the sum of all cell values in the neighborhood.
    • Variety: Counts the number of distinct cell values in the neighborhood.
    • Range: Computes the difference between maximum and minimum values in the neighborhood.
    • Majority: Determines the most frequently occurring cell value.
    • Minority: Determines the least frequently occurring cell value.
    • Median: Finds the median value after sorting all cell values in ascending order.
  • Neighborhood Shape Types

    Four neighborhood window types are available:

    The diagram below shows the four shapes with default 3*3 neighborhood size. Cells are for illustrative purposes only.

        
        
    • Rectangle: Defined by specified width and height (default 0 in geographic/raster units).
    • Circle: Defined by radius (default 3 units). Cells partially within the circle are included.
    • Annulus: Defined by inner and outer radii (default 3 and 6 units respectively).
    • Sector: Defined by radius, start angle and end angle (default radius 3 units, angles 0°-360°).

Feature Entry

  • Spatial Analysis Tab->Raster Analysis Group->Raster Statistics->Focal Statistics.
  • Toolbox->Raster Analysis->Raster Statistics->Focal Statistics.

Parameter Description

  • Source Dataset: Select source raster dataset including datasource and dataset.
  • Parameter Settings: Configure focal statistics parameters:
    • Statistical Mode: Choose from 10 modes including Min, Max, Average, STDEV, Sum, Variety, Range, Majority, Minority and Median.
    • Unit Type: Select between rows/columns (raster units) or map units for measurement.
    • Neighborhood Shape: Configure dimensions for selected shape (Rectangle/Circle/Annulus/Sector).
  • Ignore No Value: When checked, excludes NoData cells from calculation.
  • Result Data: Specify output datasource and raster dataset name.