| # GRASS Help System

## BUILDING CUSTOM FILTERS

The user may wish to model interactions across a landscape or remove systematic distortion occurring across a map or image. Both applications can be accomplished by filtering data. Custom filters can be built which make the value of one pixel a user-defined function of the values in the surrounding cells.

The GRASS programs that can be used to build custom filters are:

- i.zc
- r.mapcalc
- r.mfilter
- r.neighbors

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

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Automatically created on: Sat Jan 8 06:50:27 2005