# GRASS Help System

## NEIGHBORHOOD ANALYSIS AND FILTERS

The user may wish to model interactions across a landscape, or to remove systematic distortions occurring across a map or image. The user may also wish to eliminate "noise" from map data in order to make the basic results more visually apparent. Such applications can be approached by filtering data.

The user can build custom filters to make the value of one pixel a (user-defined) function of the values in the surrounding cells. The paper "r.mapcalc: An Algebra for GIS and Image Processing" provides examples of how some spatial filters commonly used in image processing can built using r.mapcalc. See also past issues of the newsletter "GRASSClippings" for other examples of custom filters for specific applications and the image processing section on "Building Custom Filters."

The programs below are used in neighborhood analysis and filtering.

- r.basins.fill - r.mapcalc
- r.buffer - r.neighbors
- r.cost - r.slope.aspect
- r.clump - r.thin
- r.drain - r.watershed
- r.grow

For more information on a specific command, select a command and press ESC.

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Automatically created on: Thu Oct 14 02:12:26 2004