![]() The prefix "iso-" can be replaced with "isallo-" to specify a contour line connecting points where a variable changes at the same rate during a given time period. Specific names are most common in meteorology, where multiple maps with different variables may be viewed simultaneously. 1.8 Thermodynamics, engineering, and other sciencesĬontour lines are often given specific names beginning "iso-" ( Ancient Greek: ίσος isos "equal") according to the nature of the variable being mapped, although in many usages the phrase "contour line" is most commonly used.1.3 Physical geography and oceanography.In the latter case, the method of interpolation affects the reliability of individual isolines and their portrayal of slope, pits and peaks. Contour lines may be either traced on a visible three-dimensional model of the surface, as when a photogrammetrist viewing a stereo-model plots elevation contours, or interpolated from estimated surface elevations, as when a computer program threads contours through a network of observation points of area centroids. The configuration of these contours allows map readers to infer relative gradient of a parameter and estimate that parameter at specific places. A level set is a generalization of a contour line for functions of any number of variables.Ĭontour lines are curved or straight lines on a map describing the intersection of a real or hypothetical surface with one or more horizontal planes. ![]() When the lines are close together the magnitude of the gradient is large: the variation is steep. The gradient of the function is always perpendicular to the contour lines. More generally, a contour line for a function of two variables is a curve connecting points where the function has the same particular value. The contour interval of a contour map is the difference in elevation between successive contour lines. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness of slopes. ![]() In cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. ![]() A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value. ![]()
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