raster

n.
A scanning pattern of parallel lines that form the display of an image projected on a cathode-ray tube of a television set or display screen.

[German, from Latin rāstrum, rake (from the resemblance of the parallel lines to a rake's path).]

The horizontal lines (scan lines) displayed on a TV or computer monitor. This is the origin of the term "raster graphics," which is the major category that all bitmapped images and video frames fall into (GIF, JPEG, MPEG, etc.). See raster scan, raster display, analog video and bitmapped graphics.

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In Geographic Information Systems, a grid square. Raster data are spatial data expressed as a matrix of cells, with spatial order indicated in the ordering of the cells. A raster map is a map stored as a regular array of cells; a raster scanner records an image by breaking it into pixels. Raster to vector conversion consists of changing an image made up of cells (rasters) into one made up of lines and polygons.

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