MAP LAYERS - MAP LAYERS the data for an area can be...

MAP LAYERS
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the data for an area can be visualized as a set of maps of layers
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a map layer is a set of data describing a single characteristic for each location
within a bounded geographic area
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only one item of information is available for each location within a single layer - multiple
items of information require multiple layers
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on the other hand, a topographic map can show multiple items of information for
each location, within limits
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e.g. elevation (contours), counties (boundaries), roads, railroads, urbanized
areas (grey tint)
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these would be 5 layers in a raster GIS
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typical raster databases contain up to a hundred layers
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each layer (matrix, lattice, raster, array) typically contains hundreds or thousands
of cells
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important characteristics of a layer are its resolution, orientation and zone(s)
Resolution
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in general, resolution can be defined as the minimum linear dimension of the smallest
unit of geographic space for which data are recorded
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