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A scheme for storing a digital representation of a map, image, or other two-dimensional distribution. A rectangular area is divided into an array of rows and columns to form cells or pixels. Each cell\'s contents are then summarized as a single number, class, or measure, and stored in a predetermined sequence, normally row by row from the top left. Their fixed spatial resolution makes rasters more suitable for certain kinds of geographic data, notably data from remote sensing (but see quadtree). Rasters are a popular choice for geographical information system applications in resource management, but vector data are more popular in other applications. Difficulties arise in applying rasters to the curved surface of the Earth, but recent research has identified several promising ways of subdividing the planet systematically and hierarchically. (MG) |
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