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R Back to Index Raster 1) Images containing individual dots with color values, called cells (or pixels), arranged in a rectangular evenly spaced array. Aerial photographs and satellite images are examples of raster images used in mapping. 2) Method for storing spatial data that involves assigning a value to each dot in a large matrix. This method is very useful for modeling continuous phenomena like elevation of temperature. Remote Sensing Using a recording device not in physical contact with the surface being analyzed including: 1) Using sensors sensitive to various bands of the electromagnetic spectrum. 2) Assessing its spectral image without having the sensor in direct contact with the surface. 3) Interpreting environmental conditions at, below and above the surface of the earth, typically by processing images from an aircraft (i.e. aerial photography), satellite imaging (ie. SPOT), or radar. Resolution Fineness of detail that can be distinguished in an image, as on a video display terminal. 1) "Display Resolution" The density of the pixels that compose an image (See Pixels). The greater the number of pixels per square inch of screen, the greater the resolution. In print, resolution is measured in dots per inch (dpi). 2) "Spatial Resolution" The smallest possible map feature that can be accurately displayed at a specified map scale. For example, in a 1:24000 scale map, a 50 foot distance between a roadway and railroad track centerline is one fortieth of an inch. Since the thinnest pen line width is presumed to be one fortieth of an inch, it is impossible to accurately represent the alignment of these two centerlines and still have a visible gap between them. To do this takes a smaller map scale (< 1:24000). |
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