1 [spatial analysis] 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 are most commonly three-cell by three-cell squares.
2 [data analysis] A desktop GIS operation used to hide (but not delete) features in a map document or attribute table.
3 [data analysis] A constraint used to define a subset of data.