# isopleth

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## isopleth

(ī`səplĕth'), line drawn on a map through all points of equal value of some measurable quantity. In many meteorologic, oceanographic, or geologic studies some physical or chemical property is examined that varies from place to place on a map. Isopleths showing the quantity of the property being studied can be drawn on the map to highlight regional trends of high or low abundance of that property. For example, topographic maps showing contourscontour
or contour line,
line on a topographic map connecting points of equal elevation above or below mean sea level. It is thus a kind of isopleth, or line of equal quantity.
of equal elevation are probably the most common type of isopleth maps. Relief "highs" (hills) are shown by concentric contour isopleths, and depressions such as volcanic craters are shown by concentric contours with hachures pointing toward the center of the depression. Isopleths are drawn on weather maps to indicate lines of equal air pressure (isobars) and equal temperature (isotherms). Isobaths are lines connecting points of equal depth in lakes and oceans. Isopach maps show distribution of thickness of a given rock unit. Gravity maps are drawn showing isogals (lines of equal gravitational acceleration). Variations in the strength of the earth's magnetic field are shown by isogams (after gamma, the common unit for measuring magnetic strength).

## isopleth

[′ī·sə‚pleth]
(mathematics)
The straight line which cuts the three scales of a nomograph at values satisfying some equation. Also known as index line.
(meteorology)
A line of equal or constant value of a given quantity with respect to either space or time. Also known as isogram.
More specifically, a line drawn through points on a graph at which a given quantity has the same numerical value (or occurs with the same frequency) as a function of the two coordinate variables. Also known as isarithm.

## isopleth

On a chart or a graph, a line of constant value of a given quantity with respect to either space or time. Also called an isogram.
References in periodicals archive ?
They found that a cyclonic pattern of fallen trees was mainly located within the condensation funnel and embedded within EF2, EF3, and EF4 isopleths, and that the diameter of the cyclonic pattern was much smaller than the condensation funnel size.
Nevertheless, in basing the Map A 63-64 isopleth on data from two cities (West Los Angeles and Corona), we stretch credulity to the breaking point.
Within these relatively constant large-scale spatial trends, small-scale patterning was notably dynamic, as illustrated by the seasonal isopleth series for Acrobeloides and Chronogaster [ILLUSTRATION FOR FIGURES 7 AND 8 OMITTED].
The distance from the centerline to the EFO isopleth is about 250 m.
8"W) as a minimum convex hull encompassing all Ohio or Illinois badger 95% fixed kernel isopleth estimates (Fig.
This method defines the core area by taking the first derivative of a nonlinear least squares curve of an animal's UD against isopleth volume to determine when the slope equals one, at which point the proportional area of a UD increases at a greater rate than isopleth volume.
4] grasses, we used the regression models (soil texture held constant as sandy loam) to generate the isopleth of equivalent [C.
Isopleth values of 95% and 50% were used to determine sizes of home ranges and core areas, respectively.
We defined study area, home range and core area as the entire SRS, the 95% FK isopleth, and the 50% FK isopleth for each animal, respectively.
The isopleth approach is easy to use as both a general and stock-specific tool.
Core ranges were defined by the harmonic mean isopleth enclosing 65% of the fixes.

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