| # GRASS Help System

## INTRODUCTION: DISPLAY FRAMES VS. GEOGRAPHIC REGIONS

Several GRASS commands exist to manage the two types of 'windows' available in GRASS: graphics display frames and geographic regions. Although both are sometimes referred to as 'windows', the user should be careful to distinguish between the two.

What is a Graphics Display Frame?

GRASS supports the use of multiple graphics display monitors during a GRASS session. The d.mon command is used to start, select, stop, and unlock graphics monitors for GRASS display output.

After the user has started and selected a graphics monitor for output, the user can subdivide the monitor into different "frames", and display different GRASS outputs in each frame. For example, the GRASS program i.points divides the monitor into multiple frames to allow the user to target rectification points on an image to (user-known) points on another map layer. Similarly, the GRASS macro 3d.view.sh divides the monitor into nine frames to demonstrate the 3-d viewing function of GRASS. These commands affect only the display of graphics, and do not alter the user's data.

In past GRASS releases, "graphics frames" were referred to as "graphics windows"; the latter term is now obsolete.

What is a Geographic Region?

Other GRASS commands can be used to modify the settings of the user's geographic region. The settings define the geographic boundaries, map projection, coordinate system, and resolution of data sets. GRASS commands commonly ignore data falling outside of this region. For example, when the user digitizes with v.digit, only those areas of the map that fall inside the user's current geographic region will be saved to the vector file produced by "v.digit". When the user prints map output, current geographic settings are also used. Current geographic region settings are stored in the "WIND" file under the user's current mapset.

In previous GRASS releases, the "geographic region" was referred to as the "geographic window"; the latter term is now obsolete.

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Automatically created on: Sat Jan 8 06:50:25 2005