| # GRASS Help System

## THE MAP THRESHOLD

The distance indicated by the map threshold is the same as that indicated by the digitizing threshold. However, it is measured in map units (distance on the ground) and thus takes into account the map's scale. For example, suppose a map is being digitized using the UTM coordinate system. Map units would thus be meters. The default digitizing threshold of .04 inches is equal to .001016 meters. If the map scale of the map being digitized is 1:24,000, the map threshold would be .001016 multiplied by 24,000, or about 24.38 meters. A map scale of 1:50,000 would give a default map threshold of 50.8 meters. The map threshold may not be changed directly. It changes automatically with a change in the digitizing threshold.

See "Cartographic Issues in the Development of a Digital GRASS Database" (Ruiz and Messersmith) for further information map development issues.

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Automatically created on: Sat Jan 8 06:50:26 2005