# GRASS Help System

## DIGITIZING THRESHOLDS, MAP THRESHOLDS AND SNAPPING THRESHOLDS

The g.region program is used to set the resolution of data stored in raster data format. However, when digitizing vector files in GRASS, and when converting vector files to other (e.g., raster) data formats, the data "resolution" is based on the digitizing (or map) threshold and the node snapping threshold. These threshold levels are explained briefly below. Use the "ESC" key to obtain more detailed explanations of their use.

Digitizing Threshold - Determines which points are saved during
digitizing. Expressed, in map distance, as the width of the
corridor surrounding each point outside of which digitized points
will be saved.

Map Threshold - Expresses the digitizing threshold in different
units. The map threshold is expressed in units on the ground, as the
width of the corridor surrounding each point outside of which
digitized points will be saved.

Snapping Threshold - The radius within which vector nodes will be
"snapped" and said to be at the same geographic coordinate location.
Used during digitizing, when importing vector files to GRASS vector
format, and when converting vector files to GRASS raster format.
Generally expressed as a map distance, but may also be expressed
as ground distance.

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Automatically created on: Sun Mar 5 12:05:43 2006