Annulus Neighborhood Focal Statistics
Overview
This tool performs focal statistics using an annulus-shaped neighborhood.
How It Works
Focal statistics use the current cell as the focal cell, aggregate surrounding cell values within the specified neighborhood, and write the result back to the focal cell location. The neighborhood geometry controls the spatial range and directional behavior of the statistic.
Use Cases
- Analyze ring-shaped context around each cell while excluding the immediate center area.
- Summarize surrounding influence at a defined inner and outer radius.
- Use as an intermediate raster in a longer iXGIS neighborhood analysis workflow.
Parameters
| Parameter | Description | Notes |
|---|---|---|
| Input raster file | Raster file for focal statistics. | Required. |
| Annulus center X offset | X offset of the annulus neighborhood center. | Required. Default: 0. |
| Annulus center Y offset | Y offset of the annulus neighborhood center. | Required. Default: 0. |
| Annulus inner radius | Inner radius of the annulus neighborhood, in the raster coordinate system units. | Required. Default: 50. |
| Annulus outer radius | Outer radius of the annulus neighborhood, in the raster coordinate system units. | Required. Default: 100. |
| Statistical method | Statistic calculated from cell values in the annulus neighborhood. | Required. Default: nan_average. Options: sum ignoring invalid values (nan_sum), maximum ignoring invalid values (nan_max), minimum ignoring invalid values (nan_min), range ignoring invalid values (nan_range), average ignoring invalid values (nan_average), variance ignoring invalid values (nan_variance). |
| Output raster file | Output raster containing the annulus neighborhood focal statistics result. | Required. |
Steps
- Open the Geoprocessing Toolbox in iXGIS, go to Spatial Analysis Tools > Neighborhood Analysis > Focal Statistics, and start Annulus Neighborhood Focal Statistics.
- Select the input raster file and confirm that it can be read correctly.
- Set the annulus center offsets, inner radius, outer radius, and statistical method.
- Specify the output raster file and confirm the output path, format, and file name.
- Click Run. After the task completes, review the output value range and spatial pattern.
Notes
- Verify that the raster coordinate system, cell size, and units are appropriate for the radius settings.
- Inner and outer radii use the raster coordinate system units, not necessarily meters.