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Image filter

On a raster, an analysis boundary or processing window within which cell values affect calculations and outside which they do not. Filters are used mainly in cell-based analysis where the value of a center cell is changed to the mean, the sum, or some other function of all cell values inside the filter. A filter moves systematically across a raster until each cell has been processed. Filters can be of various shapes and sizes, but three-cell by three-cell squares are common.

Incident angle

The angle between a ray (e.g., a RADAR wave) incident on a surface and the line perpendicular to the surface at the point of incidence.