raster One of the two major types of internal data organization used in GIS. Raster systems superimpose a regular grid over the area of interest and associate each cell-or pixel, to use the image term- with one or more data records. The values associated with each grid cell may represent either real values or any scalar or nominal data values associated with the cell coordinates. Among the strengths of the raster method is its ability to accept data directly from remote sensing systems and to represent transitional information. Raster systems tend to be relatively storage-intensive and this imposes practical limits on the area of coverage, the resolution, or both of these. Capacity constraints are, however, becoming less significant as computer memory and storage become more powerful and as data compression techniques become more readily available