# GRASS Help System

## DATA CORRECTIONS, MAP PROJECTIONS AND DATA RESAMPLING

Satellite data can be geometrically and radiometrically corrected and resampled, and put in a standard, distortion-free map projection. Radiometric corrections compensate for variations in satellite sensor gain (affecting image brightness). Geometric corrections are made to compensate for the earth's rotation, spacecraft altitude and sensor variations. Image data take into account ground control points and map projections variations. A map projection describes the manner in which the spherical surface of the earth is represented on a two- dimensional surface and attempts to minimize distortion in area, shape, distance, and direction.

Read the section "Geometric Rectification" under the Image Processing menu for an examination of GRASS commands relevant to image rectification.

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