Quadrangle

Also abbreviated quad. A standard division of the Earth's surface area used in maps produced by the United States Geological Survey. Quadrangles are four-sided polygons of varying size, depending on the map series; for example, 7.5-minute quadrangles divide the mapped surface into quadrilaterals measuring 7.5 minutes (0.125 degrees) of latitude by 7.5 minutes of longitude, with each 7.5-minute map showing the topographical detail within one particular quadrilateral of this size. Because the boundaries of quadrangles are based on lines of latitude and longitude, the northern and southern limits of a quadrangle map are not straight lines, and the eastern and western limits are usually not parallel; the actual surface area covered by each map varies with the latitudes depicted.

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